This is correct. Congress can severely curtail the power of the Supreme Court if it wishes.

This sounds like a precedent that's bad to establish because it cuts both ways.

Precedent and norms have somewhat gone by the wayside in recent years, so that might not be a compelling reason not to act.

Given that Republicans removing the filibuster for Supreme court nominations was preceded by Democrats removing the filibuster for lower court nominations and Cabinet appointees, we already have plenty of evidence of one side doing things for convenience that end up blowing up in their face later on.

The response to the slippery slope is not to keep on sliding.