Why do you guys hate Stadia?
"Hate" is probably not the accurate word.
You're asking this question on a forum filled with enthusiasts (likewise most people who talk about games online elsewhere on the internet), who play their games on native hardware, with the lowest possible input lag, and most importantly with minimal data consumption (avg around 50-100GB per game) where the their local internet providers charge a fucking daylight robbery or sometimes even just don't feature unlimited data plans in their (regional) tariffs, and are not locked behind a paywall for current/upcoming hot features that are touted as "nextgen" (or should I say, has been a mainstay for the past 2 or 3 years in the name of "iterated consoles" or PC) like the jump to 4K resolution (native and dynamic).
When an entirely new medium is at your service (let alone a platform), that is marketed as a replacement to your consoles or PC, the existing audience (close to a billion people, consoles and PC combined), will obviously compare it with their hardware of choice, and denounce the product if the features don't match/exceed their native hardware, and also which in turn might shape the future of the medium and their favorite hobby.
This is probably not the target audience for Stadia. It's a service that will only catch up with time, through various devices of access - like TV, smart devices, PC's etc, that too in a hostile environment where an undisputed value for money game subscription services like Gamepass exists. Even PS Now at the moment (if you don't mind the 720 or 1080p resolution) seems like a better deal than a Stadia Pro sub or investing in the Stadia ecosystem.
You don't have to pay a subscription to access your games on Stadia...
You have to pay a subscription fee, for as basic as a feature like 4K resolution on Stadia. 4K has been gaining traction since 2015/2016, and is going mainstream as we speak. The adoption will be, if not faster than that of 1080p displays 10 years ago. So is 120 FPS gaming, both of which are getting affordable these days on PC's and consoles, and are not behind a paywall.