To add onto this, I also think Baby Pokemon are just poorly used as a Gameplay mechanic. Theoretically the benefit of a Baby Pokemon being introduced later is that it gives a way to make a Line available earlier in the game: a good example of this is Budew in Gen 4 allowing the Roselia and Roserade endgoal without giving the strong-for-first-3-gyms Roselia too early, or it's a sort of Magikarp situation where they're weaker but reward you something strong if you raise them up (Riolu to Lucario in mid game). The problem there is most of the Baby Pokemon are for species that either don't take that long to be available anyway, or simply aren't that strong to be worth the babying (the latter especially with a lot of Gen 2's). Some get it like Smoochum, Elekid, and Magby, but others like Tyrogue are late comers anyway.I realized that Baby Pokémon, while for marketing first and foremost, didn’t do a lasting impression that cross-gen evolutions do, with only the occasional Riolu and Toxel for non-cross-gen Babies and Gen 3 also only gave two cross-gen Babies. This makes Gen 4 the only generation since Gen 2 where there are more than two cross-gen Baby Pokémon alongside a non-cross-gen Baby on Riolu. Only Pichu, Togepi, Riolu and Toxel are breakouts while most other ends up being overshadowed except those of already strong Pokémon.
After that, there were no more cross-gen babies (at least, for now), and that is despite the fact cross-gen evolutions as a concept makes a full return after disappearing in Gen 5, nearly replaced by Mega Evolution in Gen 6 and eventually complemented by Regional Forms in Gen 7 and 8 to allow a full return starting with Legends: Arceus. How could Baby Pokémon didn’t make a full return despite the potentials for cross-gen babies? A comment for this YouTube video helped me realize something;
“Personally my main complaint about baby Pokemon is that aside from the Hitmons and Elemental Punch Trio, they were a pretty bad choice of lineup to babify. Vulpix had explicit Pokedex entries about how the newborn has a single tail that gradually splits, Kangaskhan has a baby in its pouch from birth, Pikachu, Clefairy, and Jigglypuff were already sufficiently cutesy and I see the likes of Pichu, Igglybuff, and Azurill more as grotesque than adorable. Just give Mikon/Trifox the base stats Vulpix normally has and buff Vulpix and Ninetales appropriately and they'd actually be relevant without needing to steal Groudon's Ability.”
In other words, while Baby Pokémon is a neat concept, the likes of Pikachu, Clefairy, Jigglypuff and Marill already makes a great job for being small, somewhat weak critter that we would love to take care off, so an even weaker form is not only redundant, but also caused raising our companion more of a pain than it should. There’s also missed opportunities as far as the second Generation such as a Kangaskhan baby as it’s own, indepedant Pokémon that GF have yet to fix this issue.
Overall, I feel like it’s an unfocused concept that only solidifies at the fourth Generation before being dropped nearly altogether, only reappearing as Toxel in the eight Generation. While Baby Pokémon as a whole can still sell well for merchandising, I wonder how much more well received they would be if they focused on making already Pokémon available earlier by making Baby form for them in the first place.
Also this is me being a stickler, but Toxel being a Baby Pokemon is dumb. It only fits the definition because it can't breed but nothing about its availability or strictly-Level-1 movepool feels like it fits the design purpose of a Baby Pokemon. It just seems like a basic stage weak Pokemon that they took the Egg Group off of because they took the "Baby" idea to a literal extreme.