A good developer should try to get a wide variety of exposure to different technologies and roles if they seek any kind of career progression. Being a Jack of all trades is actually quite useful if you want to take on a lead role as a solution architect or team lead. If you just want to stick with one tech stack you are betting your entire career on it. Eventually that tech stack will become tired and out of favour and the jobs will dry up.
That said I do think there are some people who want to change technologies like they change their underwear and that’s not great either, there needs to be a middle ground.