Frankly no one wants to hire an engineer who highlights technical debt or a lack of tests without being asked for it. This kind of negative people is annoying and IMHO is indeed a reason why employers hesitate to employ older employees. Many are a pain in the... (and I say that as someone who's turning grey as well)
Most employers want to hire someone who actively improves things, someone who solves issues, and not someone who just complaints about them and makes demands.