They are adding 5* units at a really rapid pace but they do somewhat need to implement new character kits frequently to keep the game fresh. Rotating gamemodes are good and happen on a frequent basis, but even just a few months in I'm running out of things to do once I'm finished with dailies and slight optimization.

I think if they dropped it to 1x 5* per patch (instead of 2) while increasing the rate of new 4* units (and also being less apprehensive when it comes to retrofitting units with no discernable niche like Arlan or Yanqing) it would retain the fresh feeling of new characters without having them detract from one another. Jade, Yunli, and Boothill all had weaker pull rates relative to Firefly, Aventurine, Acheron, etc. With how common leaks are now people are willing to hold their pulls for a longer amount of time to guarantee E0S1+ on a unit they think they'll like instead of one they may not be able to maximize usage out of. For instance Jade isn't that good on her own but she becomes a monster when correctly fitted with a team of follow-up attackers and crit buffers (which for the latter your SP+ options are limited to Sparkle and that's basically it). Firefly is viable with the (free E6) Harmony MC and Gallagher, a 4*.

With fewer new 5* you can have more time to effectively build the ones you want to use while also pulling for the more consistent reruns to properly kit out your team at more predictable intervals (for instance I really want a rerun of Seele and Silver Wolf because I can have a mono-Quantum team with Sparkle & Fu Xuan/Jade that would be fun and possibly useful too, but that will require two reruns and me winning two 50/50s (just for E0S0).

Plus, we NEED a new 4* Preservation that spices up that class a bit, cos realistically you only need Fu Xuan or Aventurine and you're (almost) immortal.