Personally, I don't mind a little homebrew at all but most of Larian's homebrew is extremely gamebreaking. Thief is just borked in general.
Everyone getting use item, disengage and hide as a bonus action. Completely breaks the point of going Rogue or Thief, plus game balance action economy.
Scrolls used by any class. Another jab at Thief's class feature of using any magical item or implement (this includes scrolls) regardless of class.
Thief getting a second bonus action. To compensate the class by letting everyone use their features, they can now get a second off hand attack. But wait, off hand attacks still get full bonuses without any feats. So, 3 full attacks and Sneak Attack bonus (easily procc'd just by being behind) where a fighter using a greatsword just chills at 1.
Second Story Work just being fall damage resistance. No jump distance or anything. I get that there is no climbing (there should be) but the obvious bonus that WOULD work is right in its description but nope.
Why cant I sneak attack off thrown weapons like daggers or on bonus attacks? It should just auto proc when applicable. If you miss the sneak attack then you are SOL where as RAW you could get it on any attack action once a turn.
And thats just on Thiefs. Not to mention problems with the other classes. Namely Wizards. Chief problem is that they can learn ANY spell with a scroll, regardless of it being in their class spell list. Healing word after you Fire Bolt? Check. On that note, using 2 spells requiring spell slots in a turn is a big no no and a horrible balance issue. Namely Misty Step plus any other powerful spell (think Misty Step + Fireball shenanigans). I guess that last point is a bit moot seeing as playing this game is like playing turn based Mario, with everyone bunny hopping around everywhere....
You cannot even flank in 5e RAW, you cant do it! you cannot flank, you cannot charge you cannot distract an enemy. None of these thigns are possible in RAW outside of feats (which are not in the standard RAW mind you) or class features. 5e is a TERRIBLE tactical combat game.
So uhhh, flanking is a provided optional rule in the DMG. The Help action can be taken to give an ally advantage on an attack. The description upon doing this is that you distract the enemy. You wanna talk about knowing RAW but clearly haven't read all the source books. Feats may be "optional" but I challenge you to find the one DM that doesn't allow them. Adventurer's League allows it, and that's the official DnD League.