You are right about the Senate which is why the few who are helping confirm people need to stop.
The problem is that the main mechanism Trump is using to consolidate power is NOT using the legislature. He is making illegal moves inside of bureaus under his purview. All of the mechanisms for Democrats to check them would require bipartisanship to execute. In the house, all committees are headed by Republicans. When we talk about what they can do, thats talking about the legal mechanisms. Trump is going around the back. its no longer in their hands anymore to stop him like it would be if they were able to impeach and remove him.
All of those moves he is making can be reverted 4 years from now by a Democratic President. So yes, we have to suffer for at least 4 years, unless he is impeached or messes with the C.I.A. too much. So the Democrats need to be putting together a strategy to take the House & Senate to pave the way for their President to undo what Trump and his minions are doing.
Also, heading committees give a lot of power, but they do not give them extra votes. So in the end, while they can easily stop bills being put forward by Democrats, they do not have the numbers to get their bills passed into law (exception on budget bills) if the Democrats have the mettle to stop them.