Also resonates with me. I helped my previous company scale and get acquired and then helped scale the new team some more. Then decided I wanted to go into a high-caliber start-up because I was kind of burned-out and after a year I did. I work with brilliant people, building a product that democratizes investing in my small EU country and seeing a company grow again is fun. The problem is we lack excitedness and the feedback loop is bad so my motivation hasn't picked-up. What helped me is a new hire that brought some emotions and excitedness to the team.
I have also been thinking of giving my notice for a while now, but I'm also struggling with finding a purpose so that part also hit me hard. I'm actually scared of leaving my job in case I find out it was the one thing that gave me purpose and I won't be able to find something better.
Congrats on doing it, and please do send a message if you do find something that gives you more purpose, it will greatly help me.