We saw Dawn, a lot, but probably she’s one of the more popular girls and to tie in with the heavy DP promo. I was a little disappointed they never gave her substance other than to spur on Chloe though.
The thing with Dawn I feel is that her arc throughout DP was very much conclusive by the end of the series and she had all of her character development in her own series itself, so she doesn't really have anywhere else to go as a character except to maybe become Top Coordinator, which isn't a conclusion they seem to be willing to give anyone (ie have them fully achieve their goal), barring Lillie due to the nature of her story. Like don't get me wrong, I would have
loved if it turned out that Dawn did win a Grand Festival and became a Top Coordinator, but they don't want to do that because they want to portray just about everyone as constantly on a journey and still working towards their ultimate goals, and in Dawn's case, to become a Top Coordinator
is her ultimate goal and to do so would mean her journey effectively would be completely concluded and over and she would have a reason to stop travelling completely because she would have nothing to work towards anymore.
So any time she ever could return post-DP she's just basically there to be her fun and lovable self. She's a fully realized character who at this point can only really just contribute to other characters and have interactions with them, because we all know as far as her own journey is concerned she's just doing her usual thing of travelling regions and competing in Contests and so it's not really worth bringing up in a significant capacity: her character arc already had its resolution at the end of DP and the only thing they can do with her now is have her be a Top Coordinator, which in their eyes would likely lead to her...not actively having anything to work towards anymore.
In general while in part it's because I love Dawn and she's one of the most formative characters for me, I did like her returns in Journeys overall. Her first return in the summer two-parter was pretty fun, and she showed her experience as a veteran traveler and Coordinator with Chloe, and she showed her development from DP in little, albeit neat ways. She mentions that she's competed in multiple regions like Hoenn, Unova, and Johto in addition to her home region, highlighting the fact that she's an experienced traveler and Trainer, and she mainly shows Chloe the sheer fun of being on an adventure, since Chloe's thing during this two parter was this being the first time she went on a journey/adventure on her own. From a little thing like immediately dealing with her and Chloe's bed-hair when the woke up with messy hair in the morning and taking it in stride (early DP Dawn would make a big fuss over her appearance and refuse to show herself to anyone with her bedhead), to taking the travelling in stride and enjoying the little things around her on the path (Chloe starts out very practical and restrained, focused on the destination, not the journey and the things you can enjoy along the way), which while led to Chloe being resistant at first, she eventually takes things in stride and learns to just have fun with her friends, especially at the end with Goh and Ash. And she also shows a Contest appeal with Piplup to introduce Chloe to the world of Contests, basically the idea of doing things with your Pokemon. It's a relatively simple return but she shows her experience and the development she had in DP in little ways.
Her subsequent returns were largely a BDSP special and PLA special but she shows her experience by jumping in to save the day along with the other heroes during her returns. They focus more on her protagonist side in a way, but she as usual contributed to saving the day and doing her part. Her last in-person return was being a cheerleader for Ash in the stands during his big climactic battle with Leon, tying into her being the cheerleader during DP on many occasions, and since Chloe was there on Goh's behalf since Goh had to dip on Ash last minute she stuck with Dawn since they were close.
But yeah, in any case, her returns were simple, but they were fun. She didn't show much change admittedly, yes, but that's because she had all of her character development in DP itself and there was nowhere else for her character to go except for her to reach her ultimate goal, which would effectively mean she has nothing to work towards anymore and they don't want to do that for anyone, including Ash himself as today's conclusion proved.
It's in stark contrast to say, Serena, for instance, where the way Serena's character was written off at the end of XYZ left room for her character to develop in a certain way. Her resolution at the end of XYZ was figuring out what she wanted to be a Performer for, and she decided that her reason for wanting to be a Performer was that she wanted to become someone who was like Aria: someone who could inspire others, to help others and give them the push towards their dreams. Someone who can give others strength with her performances. Which is why she decided upon Palermo's advice to travel to Hoenn on her own and gain experience on her own terms towards that aim. And that showed in her appearance in Journeys when Chloe came to meet her, and Serena showed her character development as a natural extension of her resolution at the end of XYZ, being a role model for Chloe, being able to give her advice and encouraging her to give the Contest a shot, and in turn discover a new side to herself. Chloe took after her advice and took on the Contest Spectacular and she learned what it was like to do things with her Pokemon that she can't do on her own, and that gave her the courage and will to take on new challenges.
Serena had a lot of change shown in her return (which I absolutely loved), and that's because the writers had that ability to make that character development with her because the way she was written off at the end of her series explicitly gave her character direction to develop and in the manner it did. Her return was effectively the payoff to her resolution, becoming the kind of person she aspired to be, the kind who can give others strength, give others advice, and maybe be able to help others find their dreams.
The only disappointing thing about the finale is the Rocket Trio. So in the end, they're still following Ash around. Ash is the World Champion and 99% of the time he'll likely have powerful Pokemon on him at his beck and call, but no they'll keep on trying to catch Pikachu for Giovanni. Ride together, die together, bad guys for life.
Yeah, at this point Ash and the Rocket Trio have a relationship that has basically become an eternal frenemies for life relationship and nothing will ever change about that.
At the same time, I don't think either of them actually want that relationship to change ever. In a recent interview, it was mentioned that ironically, Ash is grateful to have Jessie, James, and Meowth in his life. It is because of their repeated antics and attempts to capture Pikachu, and him fighting them off, that they have grown even closer together, and they have gotten as far as they have now in part because of the Rocket trio. And on the other hand, I think the trio themselves understand this, and so does Ash, and so that relationship is a very ironic two way frenemy one that both sides actually value. The Rocket trio have also shown in many ways that they do care about Ash and like him, and when Ash is in his big League tournaments they have always rooted for his victory. Especially in Ash vs Leon, where they were there in the stands, but they were also among the people highlighted, along with Ash's companions, Cynthia, and Diantha who were shown in a montage all worrying together for Pikachu when the latter was at its wit's end and altogether hoping for Pikachu to come through and prevail over Leon.
So that relationship is gonna stay as is. Frankly the Rocket trio themselves are not actually inherently evil despite their jobs and have their good side to them, which I think is why their relationship with Ash is so distinct and in a way is basically a frenemy style relationship, and both sides would consider it weird now if they weren't in each others' lives the way they are now.
Oh well, it's not like Ash promised to see Primeape again, and it's with a trainer and his daughter who are likely treating it as family so its in a good place. 
