suppose while were talking on unpopular opinions on characters, I never understood why people called the Gen 4 evolutions ugly or how they "ruined" the Pokemon. I really like most of them, with Mismagius, Togekiss, Leafeon, Magmortar, Honchkrow, Froslass and Lickylicky being some of my favorites. I don't see how adding cross-evolutions ruined the Pokemon, if anything it made the likes of Yanma, Piloswine, Togetic, and Roselia actually good in battles. The only one I'd really call ugly is Probopass; and while I have heard people call Lickylicky ugly, I disagree. I think its very cute, especially its Platinum sprite, it looks so happy! It reminds me of a puppy who just wants to lick you, though I'm not a dog person in real life, I'm a cat person.
I'm guessing those negative reviews is probably why we didn't get any cross gens with the exception of Sylveon until Gen 8, which is sad, because I've always thought Pokemon like Swoobat, Chatot, Noivern, Lumineon, Skrelp, and Clauncher could use a new evolution. I'm also not a fan of how they handled it in Gen 8. I don't like how they are tied to the regional variant instead of the base form, because the base form of Farfetch'd and Corsola still suck despite their Regional forms getting an evolution.
Honestly? You are not the only one who have a generally good feeling surrounding about the Gen 4 cross-generational evolutions. The only one I'd really call ugly is Probopass like you call it such, and I do prefer Magmortar over Magmar, believe it or not.
Cross-evolutions does not ruin Pokémon, and instead allows for better balance without getting compromised like what happened to Mega Evolution in the mainline games, while also making sense. Having Luvdisc, Volbeat or Illumise about 500 BST or a bit higher wouldn't make a mint of sense since their design suggests they
are supposed to be somewhat weak, if not very weak in Luvdisc's case. Their potential evolution, however, can make a BST as high as I mentioned making sense, and even make a sense of progression and accomplishment. That's coming from a guy who made an extremely rare fan evolution for both Volbeat and Illumise, each having a whopping 555 BST, same as Arcanine's!
The worst about the complaints regarding the cross-evolutions is simply out of blatant nostalgia reasons instead of judging them in their own merits. Like, I get it, not all cross-evolutions are winners viable-wise, but would you rather have Tangela still be a weak single-stage Pokémon?
Good news is, likely because of the overall positive reception towards Regional Evolutions, fans are starting to wanting standard cross-evolutions again, particularly for the likes of Dunsparce. The severe lack thereof traditional cross-evolutions since Gen 5 and 7 did none and Gen 6 only gave us Sylveon, also contributed to make fans to miss this feature. The introduction of regional variants helped soften the blow though.
And while it does sucks for the regular variants to still not evolve further while their regional counterpart can, this is not a major dealbreaker for me, since not only they were supposed to be their own species despite sharing basic design and name... would you rather have Galarian Farfetch'd or Galarian Linoone to not evolve further and have limited viability to the point fans calls them a waste of Galarian Form slots, or G-Corsola to not have access of Eviolite shall Cursola not being made?
Overall, new cross-evolutions should be made soon or later, especially since things like Mega Evolution and especially G-Max prove that those mechanics are not permanent solution.
... Now wanna hear something that annoys me? The opposite in that some people wanted a Pokémon
removed from an evolutionary line. That don't apply to just some of the more "infamous" cross-evos, but also the likes of Zoroark, Silvally (though that can stay as a form in a severe fan reboot), Purugly and Toucannon without replacing them would cripple their pre-evo that would make them come off as not only incomplete, but also risk of being useless and expandable. Not necessarily true for Rhydon, Magneton, Electabuzz and Magmar as they can on their own, but for everything else, this will be a severe problem if the final evo is removed.