I am employee market, yes. You make people do the things they don't want to do, they start looking for another job and quit 2-3 months after. This has been a trend in my current company, to the degree that "developer preferences" is one of major factors when choosing tech stacks.

You can say no but you will have to be tactful. A simple refusal might get you fired but asking for training or showing how you are inefficient at certain task, may send the message without embarrassing your boss.

People are pretty damn good at finding reasons why they can't do a task or can't do it well or at least can't do it now, without it being an unacceptable direct "no, won't do that". And in plenty cases, loosing employees over something like that isn't worth it, especially for companies that already struggle with hiring enough and retaining knowledge.