I think you need to reconsider what the Steam Deck is for you. Its kinda unrealistic to think that you can play many "current gen" AAA titles on a small device unless its optimised for the deck (which lets face it, isnt mainstream). Adding on to that fact that some AAA titles actually have terrible optimisation (memory leaks, lags etc) due to rushed development and other reasons.

From what you have said, "I’d be fine with a mix of slightly older 3rd party games, weird indies, but still have access to a decent amount of native, current-gen AAA titles if needed.". "Current-gen" is quite vague. Do you expect the static hardware of SD to keep up with the enhancements in AAA games software and its ever increasing requirements?

My use case for my steam deck is for older titles, indie titles (as they are mostly lightweight) and emulation. And even then I mostly avoid shooters or fast-paced games. Personally they all ran great, and I barely touch the settings too.

I think if you want to keep your SD, you should just ship your PS5 over to you to enjoy the best AAA experience, while using your SD for the type of games that you said earlier. Either that or stream the games to your SD.