You could consider splitting certain large, distinct pieces into separate services, maybe. You don't need a dichotomy of one monolith vs. dozens of microservice

You could consider splitting certain large, distinct pieces into separate services, maybe. You don't need a dichotomy of one monolith vs. dozens of microservices. You could have a monolith plus 3 or 4 services. Or only do that going forward; e.g. for future feature requests that would otherwise require adding another huge chunk to the monolith.