I used Linux before Steam came to Linux, those were the good old days where every game required tinkering in WINE. I actually didn't have a Steam account until it came to Linux, and then I played only a handful of Linux-native games (Rocket League was one of them).
When Proton came to Steam, a whole new world opened up, and now I can basically assume a game will work and I'll be right more often than not.
So from my perspective, it wasn't a rocky start at all, but a gradual widening of my gaming library. I've since played a ton more games, so I've rewarded Steam for the effort.
I spent ages thinking that I'd found a title that didn't work, getting barely double-digit frame rates in the 3D hub area.
And about two months later I realised that what I'd actually done was lock the laptop into low power mode with the CPU and GPU being way underclocked and locked to that regardless of load. One metaphorical switch flip later, 60+ fps.
No its Just that at some point disk speed provides marginal improvments for most games, especialy since most games were designed with hdd drivers in mind . And sd vs ssd in steam deck are at that point.
There are exceptions to that, but they are pretty rare ( alghtough i cant remember one right now but i know i watched one comparison where nvme disk provided actual reasonable benefit compared to sata so i imagine its even bigger with sd card ).
So unless you play very specific game a lot that you know benefits from fast disk speed then it dosent really matter that much.