[plam503711]

I agree. If it's already hard for simpler stacks, you can imagine how hard it is for more critical or complex ones. And it's even worse if you inherited some of it (ie collecting technical debt that's not yours, which is the case here as some part of the stack are the result of a fork).

Sometimes it's even a catch-22 situation, where the technical/generic knowledge is already hard to find, but you absolutely need it to train more junior people. Luckily we found such experimented people, but then you also need to use their expertise to actually fix stuff and not just mentor juniors. A very very delicate balance to find, especially in a timed market.