I currently have a role where I have to know a few platforms at least at a basic level. Keeping up with even reactJS changes, the newer versions of nodeJS, while also trying to learn things like kotlin multiplatform and kotlin flows for android, is pretty hard while i'm also trying to learn swift / swiftUI / uikit to a basic level. I have been mostly a backend / android dev for half a decade or so plus maybe 7-8 years before that as a c++ dev... but frameworks etc are getting so wide now its really hard to stay up to date when everyone is using so many random platforms and packages. I would say the worst really is web development where its so very flavor of the week. The mental strain of that, its just hard to keep all those plates spinning.