I don't know what you've been reading, but there's a mountain of criticism of populism – including Trump's flavour of it – and then some.

Speaking purely for myself, I would rather criticise my "own side" (i.e the left in my case) than the "other side". I feel it's considerably more constructive and helpful. It's also exceedingly vexing to see someone make bad arguments for a position you broadly agree with.