Yes. Negative difficulty curve was something that was quoted as problem in Facebook Q&A (you can still find those among early updates - can’t be bothered to find exact quote. PP was to reverse it, making game harder as it progresses - so the player starts with advantage, and enemy adapts.
FiraXCOMs progression system isn’t something I am a big fan of - it hides the shallow nature of the game, by faking player skill increase by stacking odds in favour of the player as the game goes on. Something I do like about XCOM2 progression, is how it utilizes early enemies in later stages of the game - sectoids and snakeman becoming effective support units after initially acting as the main threat. There is also the problem of the positive feedback loop - XCOMs tend to be either too easy or too hard - if you struggle you are less likely to do well in the follwing missions, and if you already do well, you will only get more powerful, making the game even easier. WotC somewhat addressed this issue with spikes in difficulty, though it is still far to easy to overpower Chosen IMO, and if they won’t hurt you they make you even stronger.
Enemies improving as the game goes on is something I can get behind - as players learn and explore mechanics game should increase the level of challenge: the issue seems to be that it doesn’t get any more interesting. It reminds me of an oldfashined way of doing difficulty - just buffing enemies with more health. That doesn’t shake up your tactics - it just limits what you can do, and makes you do the same thing more times in the row - not fun. Reminds me of playing Messiah of Might&Magic on hardest difficulty, where backstabbing was the only effective way of playing.
That is not great. Increased difficulty should encourage and test the mastery of the systems, and increase complexity of decision making; not make certain weapons and strategies unviable.
EDIT. Don’t read it as criticism of PP, as I didn’t get far enough to experience much of the enemy progression.