I mean, highly optimal double teams are really only necessary on the highest challenge levels of Memory of Chaos and Pure Fiction (like, for lower stages, you shouldn’t even bother bringing a sustain most of the time). Which is not that much in terms of how much Stellar Jade you can earn. Like, MoC, if you’ve reached the point where your party can hit level 80, you don’t need a fully optimal team to clear the first 9 stages.
And Natasha, who heals, is provided, and you can clear the whole main story with just her as your one sustain unit. Beyond that in terms of a second team, you have some options:
-March 7th is the weakest sustain unit, but she is an option
-Lynx was given out for free for doing one of the events
-Bailu or Gepard can be obtained through missed 50/50s or the standard banner
-pulling for HuoHuo, Fu Xuan, Luocha, or Aventurine on their banners
And mind you, Pure Fiction wasn’t added until 1.6, so only MoC utilized two teams. That’s one optional game mode which isn’t a big deal stressing about.