I think Ostrago that you're a great example of exactly how Larian thought after a few devs played one or two games of tabletop D&D.
That line of thinking is absolutely understandable. If you're an average character, you have +5 to hit an enemy. If you that enemy has an AC of 13, well, the math is what it is, you're chance to hit is 'just' 60%. To some people, that seems absurdly low. But that's because of the well known inability of human beings to properly grasp and understand percentages. Our brains just don't deal with them very well.
Before I discuss further, I want to bring up a point you made and one that is making this issue significantly worse: what should be relatively simple fights take an excruciatingly long time. This is almost entirely due to Larian *also* rebalancing enemy's AC and HP values. They lowered the AC so you'd hit more, but increased their HP so it would take more hits to kill them. This has the same affect on game balance as a butterfly flapping its wings, except the hurricane is literally the very next step. Fix that HP bloat problem, and suddenly lots more cool combos and spells become way more useful like they should be. Have faith in the rules of 5e.
But I digress. You are right, a lot of low level D&D combat seems to be about chasing methods of increasing your chance to-hit. It's your time to learn some additional tactics and gameplay mechanics beyond just swinging a sword or shooting a bow. It's a great time to learn ways to buff your party, how different class abilities can be really valuable, what sort of spells (the guaranteed damage ones) are super good against high AC enemies, and which spells are great against low AC enemies. Basically, it's time to learn how to play the game, what the different classes (and subclass especially) are good at doing and what they're weak at doing. Your Wizard might be great for blowing up large numbers of weak enemies, but not great against single targets. Maybe your Ranger can do fantastic with bows, but suffers if an enemy gets up in there face.
Larian has basically taken all of that away from you. They've taken away dozens and dozens of class abilities and spells, and replaced them with two mechanics that require nearly zero effect or learning. Combat at level 1 is going to be the exact same as combat as level 10, literally, because all that will matter is getting above your enemy or getting behind them. Advantage and Disadvantage are the strongest mechanics *in the game*. By handing them out for free, Larian has removed all need to learn...literally anything else.
The most important thing to remember is that D&D is a *team game*....even when you're playing by yourself. Because yeah, it might be several minutes between your Fighter getting to swing their sword or your Rogue to try stabbing someone. That's a consequence of going from RTwP to TB (which I enjoy personally). But in between you have your other party members doing their turns. And yeah, maybe this combat one or two of your party members aren't going to be very effective, but you aren't playing those characters. You're playing your *party*. In DoS, every character rapidly becomes the ultimate versatile character, able to do a bit of everything really well. Every single character can heal, can have high mobility/teleporting, can dish out huge single target and AoE damage, and is capable of disabling all enemies. In short, each character may be slightly better at some things than others, but no class has a weakness. That's not D&D. You play your party, not your character.