I'm lead engineer on my startup's project, not the CTO but reporting directly to him. Team of about 30.
There are of course many legitimate things that can be described as tech debt, files that got too large and convoluted over many patches by many people, that sort of thing. But I find I have to watch out for the concept of "tech debt" because a few engineers will abuse it if given the chance.
For instance they will insist that code that was just written fresh by a colleague is "tech debt" because they would personally have written it differently, when there are no meaningful differences between the two approaches.
They can claim that a design they don't understand the reasons for immediately (regardless of whether it's documented) is tech debt.
They can claim any feature they don't personally want to do or which is perceived as hard work will create tech debt. And so on.
I wrote the initial code and I'm close enough to the codebase still to be able to fairly thoroughly examine claims of tech debt. I'd say most such claims are actually not a big deal and do not justify any non-trivial investments of time to resolve.
Moreover the sort of engineers who pay down more than their fair share of legitimate tech debt are invariably the ones who complain about it the least.