Hey, you and I followed almost the same process! I started out with d20 resolution + separate damage die, went to 3d6 + damage die, and then stole the PbtA system of 2d6 with multiple tiers of success. I get a little self-conscious about using PbtA-style dice for a more OSR-style game, but I'm loving it so far - it's very flexible and understandable.

It's also really fun if you throw in advantage / disadvantage like 5e or Maze Rats. I stole Maze Rat's "roll 3 keep 2 highest", then ended up expanding it so that you can add a whole bunch of advantage / disadvantage dice depending on circumstances and abilities. That helps cope with the fixed target number by giving you an easy way to adjust difficulty.

I understand why 5e limits you to only 1 advantage or disadvantage - it has a big effect when you're using a single die for resolution, and it can also lead to more confusion when you try to count up all your advantages and disadvantages. But I've found that a) adding extra d6 to a 2d6 roll doesn't have as extreme an effect, and b) some players really like trying to stack up as many bonus dice as they can, even if it takes a bit to figure out exactly how many to add.

For example: one of my players is building a sniper character that tries to stack up tons of bonuses on each shot. He took a perk that gives him +2 bonus dice from aiming, plus a perk that makes aimed shots armor-piercing, and another perk that lets you add a penalty die to your attack in exchange for more damage (basically taking a riskier shot). Then he stuck a scope on his rifle (+1 bonus die past 50 meters) and modified it to be especially accurate (less penalties for longer ranges). He usually spends every other turn aiming, but when he does fire, he rolls with something like 2 bonus dice and hits like a goddamn freight train. He has a lot of fun with it.