I'm going to go against the prevailing sentiment here and say that flashback use should be kept to only useful information. Keep in mind that the content per episode and the amount of episodes are finite. When it's a choice between 2.5K renders of game vs 2K game + 0.5K flashbacks per episode, I choose the former.
The DIK founding flashback had a lot of useful tidbits such as the Tommy/Rusty dynamic and also set up a lot of things - the hell week task board result, Vinny for a possible re-entry into the game, the conversation between MC and Jill re Rusty, the later demolition of what Mr.Burgmiester paid for etc.
The M&J flashback OTOH didn't really do much at all, it didn't influence MC storming out (which already happened) nor have info vital to MC's decision at the end of that chapter. All it set up was essentially the diarrhea joke. That's a lot of render resources that could have been spent elsewhere.
Anything that can be explained in one paragraph (such as a DIK telling us why Vinny dropped out) should be IMO. ATM, I see two useful flashbacks. Jill being bullied/Sister death/first meeting with Bella (assuming they are connected) and a flashback hitting the moment we open the locked room and then fading to the present time to reveal what's inside.