But having said that, the challenge of an encounter is probably the less important factor in determining its quality. Variety of enemies, terrains, winning conditions and tactical options (on the party-side) makes for a good encounter design.
Sadly, nothing of that matters when you can win an encounter just by choosing a spell semi-at random. Basically any non-useless spell of level 3+ wins all the encounters in the game on its own. And Solasta's difficulty settings aren't really the right answer if you want a better challenge in a 5E videogame. This edition's math is so strict and precise that just jacking up the numbers completely denatures the experience. Also, avoiding min-maxing isn't really an answer, unless you're actively gimping yourself with completely unviable characters like a Wizard with 8 Int or a Rogue with 8 Dex.
But don't get me wrong, I loved this game. I spent hundreds of hours on it, playing the campaign multiple times and many custom modules, and I plan to play it again as soon as they release the Primal Calling DLC. It's just sad that they could have done so much more with the system they implemented, and I hope the creation tools will give enough freedom to prove that.
Honestly, this seems like a problem in the official tabletop modules too. The system has a hard time accounting for the huge power jump PCs get on level 5 (and same for 11). So the typical challenge in modules looks like this:
By finely tuning encounters, you can easily create very interesting challenges for characters of level 5+. Official modules usually fail to do that, but it isn't hard for a semi-experienced DM. Sadly, once characters reach level 9-11, they can basically face ANYTHING in the Monster Manual (and WotC designers know that, since they aren't afraid to put level 11 characters against CR 20 enemies), and after that it becomes hard to create an appropriate encounter.
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