How to look past the fact that I probably have chosen the wrong research area? I am a computational materials science researcher. I model additive manufacturing process using continuum modeling methods. Almost everyone who works in my field are part experimentalists and partly into computational modeling. Though with an experimental master's background, my PhD research was completely computational and not theoretically intensive (it was very straightforward if one knows the computational modeling tools and a bit of coding beforehand, more like clicking the right button and developing scripts to do some analysis).
I feel that I would have gotten better job prospects if I had an experimentalist and computational profile. Almost at the end of my PhD (about to defend), I have a postdoc offer with my current PhD advisor, which I will take because I don't want to move to a different place with covid-19 in other locations. But I dread job prospects in my limited experience and expertise. How to address the fact that I might have chosen wrong research area?
Don't think of yourself as stuck in a research area. You are starting to gain some independence and can also start to morph your research into any area you choose. Over your career you might do this multiple times, actually.
Use the post doc to start to explore the areas you'd rather work in as much as you can.
Staying with your doctoral advisor might not be your best move, though with coronavirus it may be necessary in the short term as you note.
Your PI for the post doc might be able to give you some freedom here. But even if not, increasing your reputation in one area can lead to more freedom to move and change your direction.
Your career needn't be an arrow.