i get the frustration. but it's intentionally that way. the game depends on prioritizing choices like that. if you get decent backups, you'll be fine minutes-wise. (starters will be at 35-40 min regardless of blowout or not). or you can forget about better backups & train GS if you value it enough.
I'm not talking about tanking for a cup game. I have to tank in week X even if my cup opponent is a bot because I will lose 1 game badly and my starters will play 45 min, killing GS. I can either play them in both games and kill GS or play in 1, tank the other, and destroy the bot team. When I blow out a team badly, my starters play 24-32 minutes, but when my starters get destroyed, they play 45. That's a mistake, IMO. My starters should not be playing the 4th down 50 unless I want it that way (for training).
This distorts the league. For instance, say I have 2 games I cannot win this week, one versus you and one versus someone else. I tank versus the other guy and play my starters versus you. Now he gets a big PD advantage over you even if your teams are about equal quality. My hands are tied and I'm flipping a coin (or maybe home/away thing).
In blowouts, my starters should be below 36 minutes unless otherwise instructed. This would help with random tanks, IMO.