Additional problem for a senior full-stack devs is that you'll usually be assigned at solving various tricky issues, and even when you get to dig deeply into so

Additional problem for a senior full-stack devs is that you'll usually be assigned at solving various tricky issues, and even when you get to dig deeply into something and get a decent expertise on that niche, it's very likely that as soon as you setup everything you'll have move to work on something else, usually completely unrelated. After a few months of working on something else you'll almost completely forget the most of those little insights and details that you previously learned, and you'll be back at the start...