I guess this means the QA tech stack and not the Dev tech stack. I think that the importance of the tech stack depends on where one is their career and what are their next career goals. It might also depend on one’s financial goals and desired work locations.
The QA stack matters a lot to me now. I feel I am still early in my career. So, I want to be in a tech stack which has been around for a long time, continues to be improved, has lots of learning material, stack overflow questions etc. Once I figure out “general problem solving” with one tech stack, then I will feel more confident to try others. Additionally, I avoid tech stacks which have low code or no code tools. It generally feels like we work for the tool instead of the tool working for us.
As an aside, if you want to convert to Dev, then tech stack can matter. If you want to be a backend dev, then maybe you should not take a frontend tech stack. Remember that you also have to pay your bills. So, maybe avoid tech stacks which are dying or likely to die. If work location matters, then probably avoid an uncommon or exotic tech stack. Its most likely to be used in big city companies & hence a problem if you want to move to a small city.