Some of the joy in games comes from learning the boundaries of what you can do within the rules and then pushing on those boundaries. I think that Larian wants to give players that "I'm clever - I came up with a workaround that just skirts the rules" feeling, but the problem is that they give it away for free.
Blowing up barrels, for example, isn't clever - it takes work to get through the game without having barrels blow up. And once you learn that trick, it's easy to use it again in any fight. Gaining Advantage by getting to high ground isn't clever - it's almost trivial and creates a huge swing in battles; and you can use it in every fight. And even if you don't intend to use it - even if you try not to use it - it's still baked into the system and it will be used, both by you and against you.
The challenge of coming up with clever tactics isn't there - it's too easy because they are given to us for free. We need to be pushing against the rules to earn our victories. Saying "just don't use the cheesy stuff" leaves us pushing on a rotten wall that collapses under our weight. It's not gratifying.
I would get more satisfaction from the simple action of engaging enemies with a Fighter to hold them in place than the high ground backstab help jump around nonsense. But even that basic tactic isn't available since Larian gave every enemy some form of teleport. Minotaurs - teleport, Hook Horrors - teleport, Bulette - teleport, Phase Spiders - teleport, Githyanki - teleport, Mud Mephits - teleport, Hag - teleport... bla bla bla everything teleports to pounce on your squishy party members.
And all the battlefields are wide open spaces where you are just dashing for high ground. Even underground every fight is about high ground.
The OP homebrew mechanics override all interesting class ability combos like Hold Person and Inflict Wounds. Or even just shoving something prone so your team mates can use some powerful attacks with advantage would be fun, but you can't even shove prone. Just get to high ground and you'll win.
I'm surprised the combat is so terrible I don't feel like playing this otherwise amazing game.