He's done a lot. His administration has made some substantial changes despite Republican efforts to block
everything.
That being said, Americans have very short memories and they do not understand or properly attribute some of the things that have benefited them and theirs specifically. It's much easier to complain about not getting a whole pie than to compliment the one piece that you had.
FPOTUS Trump's super power is WHINING and his supporters are largely whiners. They would complain about finding a bag of money because they had to bend down to pick it up and the $20s weren't banded. He feeds that with no real plan to make things better.