Something to consider is a monolith can have different entry points and a focused area of work. Like my web application monolith can also have email workers, and background job processers all with different container specs and scaling but share a code base.

And coming from a background where I work heavily with Postgres a bunch of smaller segregates databases sound like a nightmare data integerity wise. Although I'm sure it can be done cleanly there are big advantages with having all your tables in one database.