I haven't seen this come up a lot, but I think the raid designers are becoming more skilled at designing these raids to have a fairly narrow range of acceptable solutions. It's been a lot of fun to try to "solve" this raid, and see what other people come up with.
I also think that Bug Mew working so well for randomly-matched raids was intentional. To an extent, it looks to me like the raids are about using strategies outside the norm of regular or PvP competitive play--and I don't think I've seen Tera Bug thrown around for much other than Lokix or something similarly very niche. Even if it wasn't intentional, I find the reign of Tera Bug Mew pretty funny.
There's surely a bit of "experience gain" in this scenario.
I'd assume one of the big questionmarks expecially when designing the first few raids must have been "how players will deal with it".
Charizard raid was overally pretty simple and just had players use whatever resist with high special defense.
Cinderace was given ways to buff itself and people complained of how both needed strictly specific pokemon & even then was just very frustrating and rng.
The Pikachu raid then was all about this massive shield to break while for the love of arceus not spamming Miraidon.
Then the following raid were progressively more tuned to:
- not have pokemon that completely invalidate their existance (bar some funny oversights with the AI like Dachsbun on Delphox) by nulling every attack or taking negligible damage
- not have infinite buffing and rather have specific buffing benchmarks for the players to deal with
- have a clear gameplan (some where pure bruteforce, some had you figure how to deal with their buffs, some others were about solving which pokemon can actually deal enough damage to beat the shield
- force you to think outside of the box from what you'd be doing competitively or even casually (which is also one of the reasons casual struggle with it, ha ha supereffective go brr doesn't quite work)
- give room for people to play support instead of full offense, which incidentally allows even people who havent got a reserve of exp candies and whatnot to partecipate as support mons are relatively easier to build around and play
The Mewtwo raid was definitely designed with the idea that you'd have or at very least want to use Mew. I'm not sure they specifically intended *bug* Mew to be the thing, but the intent of wanting you to use Mew was pretty obvious from both the announcement itself (with the hype video + mew itself getting the massive stat boost) and the raid design, as due to the specific coverage chosen, on anything that isn't a psychic type or gholdengo you have to facetank Tera boosted Psystrike coming off Mewtwo's 154 spatk, or supereffective Aura Spheres.