IMO foreign key constraints are bad; they make migrations and maintenance a nightmare. It's better to have application-level processes in place to ensure data consistency. I don't agree that "no foreign key support" is a good reason to not use a particular solution. Pricing concerns are valid though.
That is a strange take tbh. For me, ensuring data integrity at the database level gives me a lot of peace of mind. Migrations are actually safer and easier because the database will complain if something's wrong, and at the application level I can do an opportunistic insert and if the FK is not valid, I'll get an error, which is really nice if I don't need the related record at all so I don't need to fetch it first.
With foreign keys, I can't use https://github.com/github/gh-ost for zero downtime migrations. Instant deal breaker, because schema changes are inevitable given business evolution.