I can tell you that many people left, and after years small groups of former co-workers formed at various other companies.
However, I don't think anybody would even try to bring anything from the old job if it's not worth it (technically/professionally) Nd valid in general.
It's frustrating that too often management don't see the problems everyone else sees, and would rather waste $£ on recruitment than retention.
I left both of my last jobs for these reasons. It became a waste of time to go voice these concerns when my time would be better spent looking for a new job.
I had a discussion with my manager about this the other week and they asked me to let them know if I was considering other work so that they could try to fix it - my response was that I didn't think that would help. By the time I'm considering another job it's _because_ I no longer think my manager can or will do anything to fix the issues I have.
People generally don't leave companies when they feel like their manager would have been able to solve their issues with the company.
I can't read minds. I need people to tell me what works and what doesn't for them. An employment is a continuous transaction, if the situation changes it is absolutely open to re-negotiation. It's on both the employer, the direct manager and the employee to make sure everybody is happy with the arrangement.
And the two times I did hear about problem before the new contract was signed, I was able to find a solution. In the other case there is not much I can do.
One problem I've noticed is the sort of person who wants to apply for management roles is often the exact sort of person who should never be given that role.
It's honestly a bit rough having to rebuild relationships. I'm working in completely new technologies, which is one of the reasons I decided to move, but it's kind of difficult to go from a place of 100% trust of your peers to uncertainty about how they perceive you.
I've still been seeing some of my old team on weekends.
I think this is the key to it right here. The ones you chose not to leave behind were friends, not peers. After almost a decade, they probably are more family than friend. The rest of them though? Not even close.