A service oriented architecture is not a bad thing. It has its benefits as well as it’s downsides. The key is to know when to use the pattern and when not to.

I’m not sure what exactly “modular monolith” means but I’m guessing it’s some kind of mono repo with different services that share a large core but can scale independently. At Shopify’s scale I doubt you can just use a single service and database and not run into problems (both technical and development productivity wise).