Been there, done that, got rejected. As they always point out - like here in (2) - "YC looks for good potential founders" it must have been me (or us back then), not the project.
This is interesting but seems to not be a "database". This is a newsletter with links to other's stories. Is there any way to access this in a database-way, not a newsletter-way?
In an article on Medium in March 2021 the Blockchain startup Reef documented their experience with Alamada. After they became suspicious they cancelled the deal with them.
Them, FTX & SBF tried to destroy their reputation. Quite bold to take a stand against Alameda back then.
If you look into the source code you'll find a link to adventurega.me/bootstrap/ where it was supposedly cloned from through HTTrack. This redirects to a Typeform though asking things like current living situation in Germany and German-Russian relations. I don't get it.
In 20 years in coding PHP going from the code style you described to what you want I have never seen it going well when a new tech lead comes in and wants to rewrite everything (always worked in similar settings though where human resources are limited).
This code is making $20mio, so something must be going well. Don't forget that a codebase like this covers all the history and knowledge.
So first make sure that you appreciate the work of the current team. As you write "resistance to change is huge" I would bet that the team doesn't feel like you're trying to understand them.
It actually reminds me of a client who I wrote an order system in PHP that made $15mio annually. As the client and me didn't get along anymore he was looking for someone to replace me, and found this new CTO who came in with "everything's shitty, nothing works, we need to redo everything". Obviously the client finally saw the chance of getting rid of me, only to ask me one month later to come back as they fired the new CTO. Seems like something was working all along :)