I once myself was in a "disengaged" state :-) What motivated me most was a co-worker, that just MADE STUFF HAPPEN, I never thought was possible by just doing it.
"Migration from svn to git? Impossible with this codebase and deployment strategy" everyone thought. He made it happen by tinkering around with tools and somehow he got it working.
"Establishing a CI? No way that is possible within our worktime"... He invested some time and made it happen.
"Code Reviews? Who needs that?" He convinced us to try it out and it was the best and most wanted Meeting we had in our whole week.
So, maybe you could try to be that guy. Make things happen, don't try to point your finger on others, just pick a problem everybody has and try to solve it. It may not work, but at least you learn something on your way. But prepare to have stamina, it needs time (about a year).
I just feel that ignoring all the pessimism takes a toll. I try to stay positive but it's very draining to spend energy to solve a very difficult technical problem WHILE other humans are around basically saying it can't be done, it won't work, if it works it won't be good enough or, which is as bad as, not participating at all.
It seems that working on increasing this "pessimism buffer" might be where I should focus.
Of course it does, everything comes with a price, but believe me, it's better than the alternative: Staying with them and becoming disengaged yourself. If this happens you waste so many time of your career procastinating instead of learning new awesome stuff that is not only fun but also good for your curriculum vitae.
I made it by leaving the company and re-thinking my focus. Leaving my comfort zone by a total tech switch (new programming language, from Backend to UI) helped me to get motivated again and my learning is to never fall for such a situation again.
I really hope you can make it without leaving, this would help everybody, fingers crossed. Otherwise, just leave the company.
Is he still at your company?
Remind yourself what salaried positions are for: collecting a paycheck so you can take care of your you and your family. They're not for meaning, or purpose, or motivation, unless you have serious equity.
Remind yourself that you're not your job.