FYI some of our people internally use Jmeter. https://jmeter.apache.org/ It's not flashy so it probably wont get the standard "we are going to milk you for data" plan
The problem then is that you have to use jmeter, it's a great example of early 2000s java desktop app user experience.
Oh and, it actually does do OpenAPI specs for REST and even mock services and all that, so I'm delighted to share that it's actually relevant to this post! :^) What are you waiting for?