D&D always had a problem with its dice and 5E is especially bad with its bounded accuracy which reduces the amount of bonuses you can stack (even with Larian bending it a lot)
A D20 simply offers a too high range of results and is too random so that every action is mostly decided by pure chance with all your abilities just giving it a slight nudge that mist of the time doesn't matter.
Other RPGs do it a lot better. Even just exchanging the D20 to 3D6 would help as you would more consistently get average results.
