It was a serious answer to a question that had not been asked. Nothing in your answer addressed anything that was seriously unbalanced. It addressed all kinds of other issues, like play style and what your players find fun and system mastery, without addressing the issue of things being seriously unbalanced.
That question had already been answered at the bottom of page 1.
Having a particular class/feat combination that can render most encounters built with the guidelines in the book ineffective does seriously imbalance the game. Especially given the fact that it is quite nicely balanced in many areas.
Furthermore anything that limits tactical choice by being the clearly superior option, instead of promoting more choice, unbalances the game, because choice is minimized, hence, less balanced.
I'm not going to go into exactly specific detailed examples because I get the feeling you're hovering around like a vulture ready to pick apart any minute detail or mistake that may have been made, whilst completely ignoring the in game context of each given scenario.
Just the fact that a 10th level character can output 100 damage per round per short rest should be enough for you to realise that this may lead to in AND out of game issues.
Or, as another example, picture this scenario. You're Bob the melee fighter and you've put hundreds if not thousands of hours into your character. You are finally reaching the higher levels. Jim the archer however in your group has decided to pick up Sharpshooter and Crossbow Expert. As you start leveling up, you start to note a lot of encounters you're pretty ineffective compared to Jim. Jim can basically do everything you can do up close and personal in combat, but he can also do the same things at range, and unfortunately for you, most of the higher level encounters you're facing happen to use a lot of highly mobile flying, or legendary moving creatures.
Poor old you is huffing and puffing back and forth, throwing a Javelin here or a hand axe there, trying to keep up. Meanwhile Jim is shooting crossbow bolts like lazers, completely ignoring cover, and doing a ridiculous amount of damage from hundreds of feet away. Soon the party basically stops buffing you completely, and they start saving their buffs for Jim, realising how much more effective he is over you.
Unless the DM start banning feats and housing ruling things, which is probably going to be very annoying for Jim, OR engineer encounters to give Bob something to do (and subsequently nerf Jim, also pretty annoying for him), you're going to end up with a serious imbalance at your table.