I second this. I lead a team of engineers, and to us the main dividing line between senior and not senior is if you're able to take on a project and lead it autonomously. I.e., you've gone past the stage where all you do is take on the next ticket in your task tracker; you have an awareness and understanding of the bigger picture, which allows you to create tickets on your own and select the most appropriate thing to work on next. The lead (me) is still there to help prioritize, fetch requirements, unblock things, etc, but it's fairly light touch management.

(Edit: my job title is Principal Software Engineer)

I'm sure you can come up with some utility class required (templated with T, Lemmy won't let me) that isn't default constructible but can be implicitly constructed from a T, then use this instead of type T in the struct definition.