I'm late, but I'm here to disagree on this one!
I find that just about every single line in Alola was directly highlighted, put in the player's path and shown off actively and deliberately, either during the story or through a sidequest. My hot take is that they did a better job of highlighting every Pokémon than any other Generation.
-snip-
Time for a late reply from me as well, I had wanted to get this done earlier but just haven't been able to. I usually like answering posts quickly here on the forums due to how fast the flow of this thread (and others) can be sometimes. Honestly, this is a reply to a post that is two pages back, even if it was only made two days ago! I remember that once in the past, I was about to reply to a post in this thread, but when I finally was about to get around to it, the thread was already several pages forward and the whole discussion had pretty much been buried, so I never got around to making that reply!
Either way, I think you made an excellent post with many good points. You are right in that S/M made a very good effort to make sure almost every single new Pokémon (and Alola form) gets their chance to shine and get the spotlight in some form throughout the games. But I don't really agree that they always do it well. Having an Alola Pokémon as a Totem Pokémon or an ace of an important trainer is a great way to give them the spotlight they deserve, and something the Alola games does way better than some other regions (notably Johto, where half of the Johto Gym Leaders doesn't even have a Johto Pokémon on their team).
However, I don't really like the way they handled all the new Pokémon in the wild. Several are just too rare or uncommon. I wanted to make a list of the Alola Pokémon and how common they are, but I really don't have the time for that right now. So here's just a short summary of the ones I remember being uncommon or rare. On top of my head, the ones I remember being uncommon were Rockruff, Dewpider, Salandit, Stufful, Bounsweet, Oranguru, Passimian, Minior, Komala, Turtonator, Sandygast, Togedemaru and Drampa. These were usually not very difficult to find as they had high encounter rates, but they were usually only found in one or a few areas. The ones I found too rare are Mareanie, Comfey, Mimikyu, Bruxish, Dhelmise and Jangmo-o. Those are only found in one or a few areas and have a low encounter rates. The worst offender IMO is Mareanie which is SOS-exclusive. I think Jangmo-o is kind of excusable though since it is a psuedo-legendary and those are supposed to be rare.
But as you also said, finding those are easy... if you know where to look and how to find them. I can't imagine the pain of trying to find a Mareanie without knowing how, for instance. This is hopefully not that much of a problem nowadays since everyone has instant internet access, but I'm still not sure. I have (or had) a buddy who is 13 years younger than me, he played Sun and Ultra Moon. He occasionally asked me how to find a specific Pokémon or thing in the games despite having instant access to everything in his smartphone at all times. I think young players these days are mostly using other sources than we older ones. I can instantly look up any info I want about anything related to Pokémon on Serebii or Bulbapedia, but do the younger players of today also know about those sites? From what I have seen, I'm not really sure.
Personally, I think X/Y and S/S did a better job than S/M at showing their new Pokémon. Sure, they might not have given the spotlight to almost every single Pokémon/line in the same way as S/M, but they did at least not make a large chunk of them as uncommon or rare. I don't think either approach is optimal though, and I'm not sure if there is a good way to showcase a low number of new Pokémon in a large regional dex.
Also wanted to say this: if we count Alola forms as "new Pokémon" for Gen 7, then we got to count Megas as "new Pokémon" for Gen 6 as well. In that case, Gen 6 introduced 3 more new Poison-types (Mega Venusaur, Gengar and Beedrill) in addition to the Skrelp line.
Sorry if this was a bad reply, I don't really have the time or energy for something better right now.
Also wanted to say this since the discussion of buying a Switch solely because of Pokémon came up. In the past, I always bought every Pokémon game, both pairs from all versions as well as all third/alternate versions, sequels and remakes. I also had two consoles so I could trade/connect with myself. Or had and had, I should say have since I still have all of them. I have one GBC, one GBA, one GBA SP, 2 DS lites and 2 3DS XLs. Was it worth the money? I'd say yes, because of how fun I had with all these games and how convenient it was to be able to trade/connect with myself without the need of another person.. Before the Switch, Pokémon was also the main reason I bought any consoles at all.
But now with the Switch, I have changed my approach. I had already decided to get a Switch before any Pokémon games were announced for it, and when I got it, my first three games were BOTW, Super Mario Odyssey and XC2, all three which I got before Sword. I only have one Switch and Sword, I have zero plans to get another Switch and/or Shield (or LGP/E, for that matter). The reason has nothing to do with money, but rather because of other factors. I have been losing interest in Pokémon recently, and Gen 8 doesn't feel worth spending a large chunk of money on compared to the past generations. The main reason being dexit and how S/S seems to have even less content than Gen 6/7. But my lower interest in Pokémon is of course a factor too, it has currently been way over a month since I last played Sword and I have no plans to return to it before November in order to prepare for the Crown Tundra. If anyone wants to buy two switches and both games for S/S, then I'd highly advise them to think more than twice about it. But if they really want to, they think it will be worth it and will spend a lot of time on the games, then I can't stop them. Because I know that feeling. After all, I used to be this type of sheep in the past.