It's a Pokemon franchise tradition to expand on evolution lines as the games travel to new regions. Throughout the series' history, Pokemon has added new forms for Pokemon to grow up into; for instance, Porygon started out as a standalone Pokemon, but Generation 2 introduced its evolution Porygon2, and then Generation 4 added its final form Porygon-Z. However, Game Freak doesn't just add new evolutions on top of Pokemon. It also introduces previous forms for established Pokemon. Fans are perfectly familiar with the phenomenon of baby Pokemon, a certain group of creatures that mark the start of a Pokemon evolution line, whether it's a totally new one or a line that's being expanded further.
Baby Pokemon have fleshed out the world's universe quite a bit. These Pokemon can't breed, but they grow into all kinds of remarkable Pokemon that may not have had lower stages of evolution before. The concept of baby Pokemon gave Munchlax to the Snorlax line, Pichu to the Pikachu line, and more. These adorable prior evolutions are all great additions to the Pokemon world, but the developer has stepped back from making baby Pokemon, favoring regional forms as a way of modifying existing lines. There's still lots of Pokemon out there that could be perfect springboards for baby versions, though.
Slowpoke
Slowpoke is an undeniably classic Pokemon. The lovably dopey Water/Psychic-type Pokemon keeps finding new ways to evolve with the help of hungry Shellder, as Slowpoke's newest Galarian evolutions indicate. However, there isn't anything that evolves into a Slowpoke just yet. It could be fun to see a young form of Slowpoke come to the Pokedex. Game Freak could take its baby form in a similar direction to Munchlax, making the baby evolution of the Slowpoke line remarkably energetic before it evolves and becomes more relaxed. A baby Slowpoke evolution could be a pure Water-type too, completely oblivious to its latent psychic powers until it starts to grow.
Onix
Onix is another Pokemon from early on in the franchise that doesn't have any prior forms. In fact, the Rock/Ground-type Rock Snake Pokemon didn't have any evolutions at all in the first generation of Pokemon. Generation 2 introduced the Steel-type, however, and in the process it enabled Onix to evolve into the Steel/Ground-type Steelix. Seeing how Onix hardens as it evolves, maybe a smaller, frailer pure Ground-type could precede Onix as a baby Pokemon. It could take the from of a literal sand snake, as opposed to the more figurative Silicobra and Sandaconda.
Farfetch'd
Just like Onix, Farfetch'd was a standalone Pokemon introduced in Generation 1. Pokemon Sword and Shield finally introduced the Fighting-type Galarian Farfetch'd and its evolution Sirfetch'd. Even so, the original Farfetch'd doesn't evolve from or into anything. A baby version of Farfetch'd could be charming. It could depict the Wild Duck Pokemon as a duckling that's still trying to master its signature leek as a weapon. Just like how Sirfetch'd evolves from Galarian Farfetch'd by scoring a series of critical hits, a baby Farfetch'd could evolve once it learns a certain move and scores a critical hit with it, signifying its mastery.
Heracross
Gen 1 isn't the only Pokemon generation with room for baby Pokemon. In Generation 2's Johto region, fans met Heracross, a mighty Bug/Fighting-type Pokemon that didn't evolve from or into anything. In Generation 6, Pokemon fans did get a Mega Evolution for Heracross, but there's still no basic evolutions for it. Lots of Bug-type Pokemon come with low-level larval versions that quickly evolve into stronger forms, so it'd make sense to get a similar larval version of Heracross that evolves once it's brawny enough.
Croagunk
The Sinnoh region's Croagunk could do with a baby version. This Poison/Fighting-type Pokemon gained some notoriety among fans after Brock caught and befriended a Croagunk in Pokemon the Series: Diamond and Pearl. Although it evolves into the intimidating Toxicroak once reaches a high enough level, there's no Pokemon that comes before Croagunk. Seeing how Brock's Croagunk had a frequent habit of jabbing him with its toxic fingers, it could be fun to see a baby Croagunk with a mischievous streak that drives it to constantly poke other Pokemon.
Drampa
One more Pokemon that could do with a baby form is Drampa from the Alola region. Drampa is unique and charming in a lot of ways: it's the only Normal/Dragon-type Pokemon in the franchise, it has a great design akin to a Chinese dragon, and its friendly senior citizen personality sets it apart in terms of lore. However, it's a little odd to imagine that Drampa acts like a benevolent grandparent from the moment it's born. Drampa would benefit a lot from a baby version that's more inexperienced and brash. To symbolize it gaining a Drampa's wisdom and kindness, a baby version of Drampa might only evolve once friendship with its trainer is strong enough.
Baby Pokemon Deserve a Comeback
On a certain level, it makes sense that Game Freak seems to favor regional variants over baby Pokemon right now. There's a lot more creative flexibility to be had in completely parallel lines of evolution than there is in the specific niche of younger, smaller versions of Pokemon. Regional variants are also a useful way to flesh out new regions without making the increasingly huge National Pokedex swell. Even so, the Galar region's Toxel suggests that the developer hasn't forgotten about baby Pokemon entirely. Toxel shares traditional baby Pokemon breeding traits with the likes of Pichu, Cleffa, and Happiny, being obtainable from Eggs but unable to breed until it evolves.
If Game Freak is still thinking about baby Pokemon on some level, then it should revisit some of these evolution lines and introduce baby forms. Baby Pokemon may not be the be-all, end-all of the Pokemon franchise, but they're a great way to introduce some nuance to raising Pokemon, and they're also generally adorable. Introducing a new wave of baby Pokemon could also be a good way to acknowledge the Pokemon franchise's history, making fans nostalgic for Generation 2 and 4's waves of baby forms. Hopefully Game Freak considers returning to this trend once Pokemon's Generation 9 begins.