Well it looks like there is a decently large drop off between your starters and subs, so that may be part of it if you are playing SFDC and are in closish games. Your starters may also have higher stamina so your bench players don't play as long because your starters are better and can play better for longer. None of this is your biggest problem though.
GAME SHAPE! All your guys are in mediocre GS. you will not win many games in IV if you don't learn to get your guys 48-70 minutes a week (Ideally 60-65 in my opinion).
Murray/Harris/MPJ/Grant/Jokic - 2020 NBA Champs