I've read bits and pieces of people saying that the reasoning is because people were missing too often, but that sounds to me like it's more of a problem with your random number generator. The average roll for a d20 is 10.5, so with a 16 or higher score in your attack stat, you should be hitting more often than not (+3 modifier, +2 proficiency bonus).
I think the root of the issue is that Larian is thinking too much like DoS 2, and not enough like BG/5e. For example, the 'missing too often' feel can be real...because Larian introduced rolling at Disadvantage at a target higher than you, or in even dim lighting. They also made the "Threatened" range about 3x bigger than the Opp Attack range, meaning Ranged characters are also going to be attacking at Disadvantage even when they shouldn't be.
They basically doubled the amount of times you can roll at Disadvantage are were surprised that combat didn't feel fun.
Wait, there's attacks of opportunity in this game!?
(Just kidding, I know there is, after all I've played 50 or so hours of it and I'm pretty sure I had one at one point...)