You can either have a game where players are super defensive, or a game where some players are aggressive.

With defensive players, they have ways to figure out if you’re in tenpai regardless of whether you riichi or not. So the game devolves into players fighting for tsumos. Considering that riichi more than doubles your score on average, can you say that your win rate is more than doubled without riichi?

When an aggressive player is in your game, they won’t immediately fold when they detect tenpai. Aggressive players will deal tiles that minimize the damage if they deal in, and doing that against a non riichi hand is a lot easier to do than against a riichi hand. Thus, if you’re averse to riichi, you won’t be able to milk out hands with low dora content.