Trump has rolled back a lot of things, yes, but a lot of the Obama-era rules were vast overreaches. Ask yourself how agencies like the EPA managed to find new sources of authority, like the authority to regulate ponds on farms, in 47-year old statutes?
Congress did not create the EPA as an agency that has plenary authority to regulate environmental issues. Such an agency would not be constitutional, because it would involve wholesale delegation of Congress’s legislative powers to the executive branch. Instead, the Clean Water Act, Solid Waste Disposal Act, Clean Air Act, etc., created specific programs to address specific types of environmental harms. The EPA is only supposed to be administering the programs Congress created.
Congress should be updating these laws to address new types of issues, but it’s not. It’s not because Republicans don’t care about these issues, and Democrats aren’t willing to spend the political capital to make these issues a priority. Whatever the reason, however, that doesn’t mean it’s okay for agencies like the EPA to creatively interpret statutes to expand their powers into new areas.