I started using Pilot.com recently and was blown away by their product (simple yet super intuitive) and their service (from onboarding to the customer success journey).
Turns out, Pilot is built on top of Quickbook Online. They didn’t reinvent the SMB accounting software. They provide a nice “wrapper app” experience to the existing software.
There are many successful services built on top of existing software tools. Pilot is one such example; My First Million podcast always talks about this guy who built a big empire with WordPress plugins; there’s a whole economy built around Notion templates; etc.
There might be new vertical SaaS opportunities built on top of existing software, by providing a superior user experience or extensions for specific business use cases.