PMC == "private military company"?

Yes

In the early days of the war back in 2014-15, it wasn't as professional due to the institutional collapse that comes with the changing of an entire political system which lead to questionable Militias being formed.

There was a lot of work on professionalizing the essentially greenfield Ukrainian Army by NATO members like Canada, US, UK, France, Germany, Türkiye, etc.

That said, a number of the unsavory militias from the 2014-15 period (such as the Azov Brigade and the Dudayev Battalion) still exist in a limited form, but largely neutered due to the efforts out to professionalize the Ukrainian Army.

The general level of professionalism has certainly not increased since February 2022. That is to be expected though. On the other hand, combat effectiveness has definitely increased.