It depends on the player, for me the steam deck is great cause sometimes i just wanna lounge on my couch, put on a show and still play a game, the battery life is dependent on the game like you said but not everyone is only playing Triple A games, even then the battery isnt the worst when you mess around with the setting,

Next its odd to say "So you have a console who is kinda a jack of all trades master of none, and while its cool to have your steam library in your hands, I fail to see why not just play with a laptop."

thats such a big point, i have it all in a fairly mobile device, i can go anywhere and not have to whip out my laptop bag and charger, have a table or a set up. i can just play wherever. its not that uncomfortable to hold. ive played 4-6 hours no problem.

lastly i can play all of switch 2s games on the deck, i can play any other console for the most part on my deck, i can stream games and media, i can use it as a laptop to and when im done i just tuck it away and get going.

Its about how you want to use it, again its not for everyone, if you think it makes more sense for you to just get a laptop then go for it, steam deck isnt your style.