That's a republican line and it's not very true in my experience. Environmental regulations get proposed and amended, it's a constant, ongoing process. Trial and error, unforeseen issues with implementation and practicality, lead to changes which are being called Trump relaxations. Backing a little bit off a future rule that tightens standards is still tightened standards, just not quite as tight as initially proposed. Generally speaking, there is usually solid justification for doing so, otherwise the industry challenges wouldn't have any merit and fall flat.
I took a quick look at this list:
https://www.nytimes.com/interactive/2019/climate/trump-environment-rollbacks.html
A lot of the stuff on there is fluff, to say the least. I'm tongue tied on what I can share on a public forum but if you want a private conversation I could go into a bit more detail on the regulations I am directly involved with. I've provided some insight in the past on a few, but those posts seem to go unnoticed. I see specifically where some of these are used politically to claim loosened regulations where the opposite is true.