I am, their height system is asinine and is going to break so many builds, it belongs in a game where everyone can teleport, not in Dungeons and Dragons
Please give us some examples of builds that you would find in the PHB that would be broken by this.
I can work through the design logic from internal testing, the monster manual goblins would be incredibly frustrating to fight with their (NOT D&D's!) elevation system, giving you an incredibly low chance to hit them with their elevated defensive positions. Furthermore, with their surfaces, it wouldn't matter because you can just throw fire
You really can't because you haven't once addressed the problems that arise when you're in this specific context; you legitimately cannot understand design if you have no idea what the system is designed for.
So they have to break more and more of D&D to accomodate their Michael Bay esque love of fire everywhere
What are the consequences right now? Concentrating on spells is MUCH harder than the original design intent. Spells that rely on fixed hp like Sleep are much less powerful than they are supposed to be (ignoring the further nerfs they gave sleep by not having it last for the full minute), spells like fireball aren't going to be sufficient to kill large groups of enemies.
To put this in perspective, since you obviously have no clue how D&D 5e works: A maximum level wizard getting firebolted by a level 1 enemy has (assumption: war caster, 14 constitution) a ~12% chance of losing concentration on their spell. Cool, really slim.
D&D was broken from the get go so stop putting it on a pedestal and actually approach this like a professional would, understand that no system is balanced especially when you try to use it in a different context.
You're also terrible because you keep conflating issues; things like sleep can be easily tuned and keep in mind it no longer has a min/max, it's simply a flat number which makes more sense for what they're seeming to aim for. But you don't even know what kind of direction they might be headed in because all you think about is how it's not 5e, so your criticisms aren't even aligned properly.
And honestly I wouldn't bother speculating about maximum level wizards or even bringing up this scenario unless you understand what they may be aiming at. And guess what? It's not a strict interpretation of 5e, they have bigger fish to fry.
(Also, your example is fucking retarded because in any given scenario there's definitely going to be gear involved).
I look forward to what other parts of this incredibly well balanced TTRPG system are needlessly changed to accommodate their desire to make another Divinity game instead of a D&D game.
I look forward to your next brain dead argument. One day, you'll be able to form a coherent argument that would allow you to pass a phone screen for an architect position. That bar is really low.
