In my experience, almost all the problems that microservices advertise solving can also be solved with a modular monolith plus some tooling to enforce certain rules (say, one module shouldn't be able to peek into another module's internals, bypassing an agreed-upon "clean" public interface; that alone solves most spaghetti-code problems)

There are two things monoliths can't easily offer:

* Using different frameworks, languages, etc. But in my experience, it's pretty rare for a team to use many programming languages at once. Usually, it's just a few highly performance-sensitive services that need to be written in another language (say, a proxy in Rust while the rest is in Python). For that, I prefer an architecture with one main monolith plus a few high-performance satellite services. No problem there.

* More optimized scaling in certain scenarios. Say I have a module that processes files and can use all available CPU. I might want to put it in a separate container on another node so that the processing doesn't destabilize the core web server. Technically, monoliths support this too, just run the monolith in a different mode (say, behind an `--image-process` flag of sorts), and you can schedule it on another node in the same way. The only downside is that it may use more RAM than necessary for the extra binaries or scripts that won't be used

What else am I missing?