Your first mistake is using the phrase “proper gamer.” What the hell is that anyway? Someone that lives in their parent’s basement, games 20 hours a day and never washes?
A gamer is simply a person that likes to play. You don’t have to know everything about modding and consoles to be a gamer no different than you don’t have to be a automotive engineer to enjoy driving. Would a Steam Deck be wasted on you? Yes, if you are simply unwilling to learn.
If you’re willing to learn how to apply mods and are willing to learn about how Steam Deck works (keep in mind, it’s a portable computer, it’s not a Switch, it’s not a console) then Steam Deck might be good for you and you can get a lot of great gaming out of it.
Steam Deck. If you have the money, the OLED or LE versions. Ally has better specs but battery life takes a beating because of those specs. But the main reason I’d never pick the current Ally or even the Legion Go over a Steam Deck is because of the support and the user experience (UX). Valve provides better support for Steam Deck and Steam OS than Asus/Lenovo/Microsoft provides for portable gaming PCs that run Windows.
Also, I’ve seen a lot of people suggest running Big Picture Mode to get a Steam OS experience on the Ally or the Go. It looks similar but it doesn’t function quite the same and features are missing. Initially I pre ordered a Ally months ago, but ultimately decided to pass on it cancelling the order. I already had a OG Steam Deck. Bought the OLED instead of the Ally.
Then there’s the battery life or lack thereof if you want to game above 15 watt. Sure, you’re going to get better performance than the Deck but your battery life is going to take a nose dive off a cliff when playing heavy games.
But hey, if you want MOAR POWAR!, go with the Ally and take your chances. You might like it regardless.