> (...) because the most experienced are needed to fire fight and to keep things running.

By that account the most experienced started out as the least experienced who built a mess, accrued more technical debt, and built up their experience keeping their ball of mud from crumbling.

They are also more resistent to change because this underlines all the crap they did. It's their baby, and their reputation is pinned on how successful it is.

New is not necessarily better, but old and stable also doesn't mean fine engineering.