L4 is an intermediary level between new-to-industry junior (new grads generally start at L3) and mid-level (L5). In many companies, it's expected that people will reach L5 within some time period.
Failing to have grown skills and project scope to L5 level after extensive time in the industry could be interpreted by some as poor motivation or career growth planning - their thinking is that if you've been doing the same thing for years elsewhere without growing, you'll tend to be trying to do the same things for years there without growing.
Failing to have grown skills and project scope to L5 level after extensive time in the industry could be interpreted by some as poor motivation or career growth planning - their thinking is that if you've been doing the same thing for years elsewhere without growing, you'll tend to be trying to do the same things for years there without growing.