I agree. While Family Sharing may be an option, it really shouldn't be necessary. Why shouldn't "I" (whether it's my dad playing Cities: Skylines, or actually me playing a round of Balatro on the Deck while waiting for a DotA queue to pop) be able to play two different games that I paid for at the same time without having to jump through any hoops? Before I knew about Family Sharing, I accidentally kicked my dad off Cities: Skylines far too many times simply by waking up my Deck.
Funnily enough, now Family Sharing largely isn't necessary because I started buying a bunch of my games on GOG which means I rarely use my Steam Deck because of how difficult most GOG games are to get running.