The more I play Solasta, the more I am seeing that Long Rest mechanics are an absolute must to figure out for BG3. Although you can't just rest wherever you want, there are rest areas in Solasta which kinda sorta limits you. Still, it's not enough. After level 5, my Sorcerer can cast Fireball and Fly, EVERY battle. Just long rest and regain them, just about every battle.
Example: I'm going into the Tower after you first go to Coperann. I fight undead. I fight wolves. I fight something else - can't remember - drakes I think. I find campsite. Ah. I can now long rest at any time in this area. By level 6 and 7, and with goodberry, I can rest anytime I want once I find a campsite. So, I fight undead at the door. Long Rest. I go into the tower. I fight ghosts. Long Rest. I fight main boss. Long Rest. I go back outside to do side quest and fight really tough undead. Pretty difficult fight, sure, but all spells in the arsenal once again. Kill him. Long rest. No real restrictions. No real limitation on spells.
I honestly don't know what the solution is, at this point, but something has to be done. Maybe the whole Earning Long Rests would be the key. In other words, as someone previously mentioned, as you complete story objectives - whatever they are - each objective awards you a certain number of Long Rest points, simulating that you've done some substantial things that day which then lead up to you earning a Long Rest. Bigger quest items that you complete provide greater Long Rest points, or whatever, so the more difficult the encounter, the more points you earn so you can Long Rest.
This would then encourage doing side quests that aren't so difficult. A bunch of easier side quests could then lead up to a Long Rest that you might need just before facing a more difficult quest.
Example: It takes, let's just say, 50 Long Rest Points to Long Rest. You crash on the beach. You meet Shadowheart and befriend her. 5 Long Rest Points. You fight the devourers. 30 Rest Points. You meet Astarion. 5 Rest Points. You encounter the fishermen and the mind flayer. 10 Rest Points. Ah. Now you can Long Rest if you need to. Otherwise, you only have Short Rests to be able to recover HP and such. (Again, Short Rests trigger dialogue. I can't stress that enough.) You meet Gale. 5 Rest Points. You find the Harper stash. 10 Rest Points. You find the chest near the ruins. 10 Rest Points. You rescue Lae'zel. 10 Rest Points, because you had to deal with the tieflings first. You face Gimblebock and company, 20 Rest Points. You've now earned 2 Long Rests, and if you haven't even used one, you're doing pretty good. You face the mercs within the crypt. 20 Rest Points. You face the traps and scribes and find the book and meet Withers and everything else in there, you earn another 50 points in all. 3 Long Rests earned by this point. At lower level, this is good. If you haven't used them all, you are storing them up for later. If you have used one or two in order to just get through, that's fine. You've still got a 3rd you can save for later.
With a game like BG3, I have to wonder if this is the only approach that will really work.