I actually like 5e at tier 4 play. You kids have no idea how good you have it. We had to play up hill, both ways, in the snow and we liked it because we didn't know any better.
I ran ad&d 2e up to 20ish (class-specific xp charts, yay) and 3e up to 23rd. 2e was a slog imo, with casters...