The "need" to be self employed only occurs in some sectors of the industry, not all.
The absolute need however, which we've all been skirting around but not stating explicitly is to really want to be there, or are en-route to what they really want to do. It really doesn't matter what job you want in aviation - maintenance engineer, design engineer, airline pilot, flying instructor, researcher - you have to really want that job and have pushed hard for it.
Pretty much any worthwhile job in aviation is filled by somebody who really wanted to be there, and has pushed for years to get to that position. There are few, if any, worthwhile jobs in this game filled by people who just fancied the job, or drifted into it.
Age is much less relevant, than how much you want the job and how hard you're prepared to work for it. There probably aren't any people posting advice on this thread who have done less than 4 years study and training since school to get where they are now, and some of us have passed 10. The only thing that'll get you through all that is really wanting to be at end point that all that will give you.
G