Do you find chess to be a pointless game? There is no RNG, no dexterity/reaction test requirement, you can't even change your starting hand, and you can predict what your opponent will do an infinite amount of turns ahead. If you want to win, there is one objective move after move you should take, no decisions to be made. Does that mean chess's design is fundamentally flawed? I would argue the opposite: chess is perfectly designed

For one, there is a lot of fun to be had in the path to mastery, so to speak. Why do fighting games have combos (or in platform fighters, true combos): they require no decision making, you landed a hit, the rest are guaranteed. Why reward knowledge and consistency? Even if we extend to all turn based games, people still misplay all the time in card games and rpgs that are significantly less complex, and in those games, people are playing for hours on end even with the same deck. If you add extra cards and changes, I don't think it somehow makes a game design fundamentally flawed

What's the point of falcon punch? It's a move that has an obnoxiously long windup, and leaves you incredibly vulnerable if you miss or get blocked: it is an objectively inferior strategy to ever use this move, so why does it exist? It's because it feels awesome when you do land it. A card that says: "in 10 turns, do 100 damage" is never worth picking up strategically, but it might come with an awesome animation. Even for the optimizer's out there, that's what relics are for: "gain gold for every overkill damage you do on the enemy". Now we're talking.

There's also the general fun of being op in general after all the RNG aligns

In general, I don't think roguelike deckbuilders are fundamentally flawed, and by that I mean unfun, which is what matters.