See, the fact that they do get an entire dex slot makes them substantially better as an idea than regular regionals to me. Regional forms may not add dex slots, but I believe they're accounted for when Game Freak is considering type balance for new Pokémon. To bring in another post:
I was a little disappointed that they didn't mention regionals too, since in my mind it's the same issue. It's kinda maybe not as bad when it's an entire evolution line, because then its usually more of a side-grade to the original (typically with a little more polish to stats, typing, and ability, though). But when it's a split evolution? That's just mean, because those new evolutions get access to the moves of the pre-evolution, regardless of how the Pokémon's concept changes when it evolves (thinking about Alolan Marowak and Exeggutor here).
Gen 8 added the lovely idea of regional forms that get new evolutions, but not the original line. It's at least a little acceptable with Obstagoon, but Mr. Rime can get all of the moves that Mime Jr. can transfer up from previous games. Even more frustrating to me is the inclusion of regional forms of Pokémon that were previously single-staged that get new evos, leaving the original in the dust. Galarian Farfetch'd at least has a new type and adjusted movepool, but White-stripe Basculin is just the same Pokémon! As the final bit of salt in the wound for me, most regional forms are added without any good explanation. Alola wasn't quite as bad with this (though Alolan Raichu is the biggest shrug of an explanation of the entire concept), but Galar and Hisui have regional variants of Pokémon that really don't have a reason to exist in their particular region over the originals (Galar especially).
All of this is for me to say: I believe many regional forms exist because Game Freak decided they wanted to update an old Pokémon concept but are too concerned with internal series consistency to change them in a meaningful way. Most of the others exist because they play off of the concept of an existing Pokémon, and for some reason they felt they needed to make these new designs regionals. They've retreaded concepts plenty of times before; very few regionals actually needed to be tied to an existing line to work. The regionals get publicity because they're new "forms," but said publicity ends up overshadowing the originals a lot.
Tl;dr: regional forms are a fun concept but are rarely necessary for whatever design they are working with to be successful.
I think opinions like these need to consider the symbolic value present in Pokemon as a whole, specifically in how we interact with it.
Consider like this, Pokemon, like many forms of fiction, is an entity reliant on symbolic value of presentation. Objectively speaking, all Pokemon
are from a purely mechanical perspective are lines of numbers activating motions in a game script, but
symbolically, they are presented as living creatures in a fictional world. These lines of numbers have visual and narrative presentation behind them which gives them meaningful worth from a holistic perspective, the belief that every entry in your PC is worth something, that every Pokemon you train and fight with are living creatures for your to value.
Consider this - why do so many players, myself include, resist or outright refuse to use Legendaries in battle? Speaking from a direct position of optimized play, the process is illogical, purposely handicapping yourself from using the actual numerically and mechanically strongest tools they have at their disposal. But from a
symbolic position, the idea is entirely natural. Legendaries are in lore presented as these all-powerful mythological (and in some cases downright divine) creatures who exist above all else in the Pokemon world, and this turns lessens the symbolic worth of using them in battle. Even though quite a few a genuinely bad in actual battle (hi Articuno), they still feel like an effective cheating device, a method of play which demonstrates less honest achievement and thus less in the way of actual satisfaction in playing the game. (This, BTW, is what separates Pokemon from a game like YGO, which has no explicitly "tiers" of overt power, and anything that is considered broken is quickly sent to the Shadow Realm/banlist)
Let's face it, Gen I has aged
a lot. The original games were not made with PvP in mind (I think Miyamoto pushed it on the team late in development?), and thus the lines were designed just as expressions of the game world, with usually bland kits that consisted mostly of just STAB moves and little else. Which was fine
at the time, but as the franchise has progressed and the awareness of competitive Pokemon and high-level play has become a core part of the franchise's identity, the complementing paratext has altered the way in which new Pokemon have been designed to better accommodate such aspects, which has in turn formed a power creep in general design which has left many of the Kanto/Johto lines in the dust. For some like Gengar and Clefable, they have the expanded kits that they're able to interact with newer Pokemon easily, but for many, the only way which they can retain symbolic and mechanical value is through explicit upgrades. Hence the use of new evos and Regionals. New evos symbolically remove the "irrelevancy" of weaker lines by establishing a higher tier of power for them to take advantage of, and Regionals allow for the symbolic rehabilitation of outdated lines into something more mechanically interesting while keep the iconography which gives them worth.
TLDR; Make Amamola a Luvdisc evo, you cowards.
