Neonchameleon
Legend
I'm going to float a hypothesis here. Almost all mature games that give any attempt at being even vaguely along the process-sim spectrum, that have survived playtesting, and that don't have designers deliberately keeping them rules light or rules medium-light end up overall at about the same "rules medium-heavy" level of complexity. This is because people aren't that different, and there's only a certain level of rules complexity that people will find fun and much more than that and the game will collapse under its own weight..
Unified mechanics are simpler, period. And addition is easier than subtraction. But it was this easiness that gave 3.X the slack to add so many modifiers and build the complexity into the 3.0 and 3.5 we all know. 4e of course added the complexity to the characters with the power structure and lots of debuffs (which had the advantage of letting it be stripped back for simpler characters so although 4e can be incredibly complex and fiddly it doesn't have to be). 5e made a deliberate effort to take AD&D rules on the cleaner d20 structure.
Unified mechanics are simpler, period. And addition is easier than subtraction. But it was this easiness that gave 3.X the slack to add so many modifiers and build the complexity into the 3.0 and 3.5 we all know. 4e of course added the complexity to the characters with the power structure and lots of debuffs (which had the advantage of letting it be stripped back for simpler characters so although 4e can be incredibly complex and fiddly it doesn't have to be). 5e made a deliberate effort to take AD&D rules on the cleaner d20 structure.