When I've used these products, they seemed to modularize and normalize each part of the pipeline separately. It's never like one "Gmail to JSON integration" and another "Gmail to Airtable integration", but instead just small modules that can be hooked together.
The input chunk (say Gmail) is one module, then the JSON processing chunk is another, then the output (like an API webhook) is another. Individual services can and do break, but the other parts still work.
If you have a workflow like "Read incoming emails, extract HTML data to JSON, extract object from JSON, transform shape of JSON, send to API", that's probably (at least) 4 different modules. If the incoming email part breaks, they can fix that separately. Likewise, you can pretty quickly hook up another output module, like if you wanted a direct connection to the Airtable API instead of a generic webhook.
I also don't know that the process of adding integrations is "quick". Zapier has been around forever and in the beginning they barely supported any third-party integrations. Make.com was previously Integromat and they also had few integrations at first – I remember requesting a bunch a few years back, when I was looking for a tool in this space.
But then serverless workers really took off and it became easy to write your own functions-as-a-service instead of waiting for the no-code tools to update.