Luckily it is open source https://github.com/Kong/insomnia so if something like that happens, a community KISS fork is possible.
I'm a big Insomnia fan and always recommend it over Postman as it's simple to use. Although even it feel a bit to "modern UI like" to me. I'd really love a old fashioned win 95 UI for this kind of thing. Tortoise git for example is my idea of a nice UI for a tool.
While we are giving tips, sometimes all you need is the fetch() api in F12 in your favourite browser. And the good think about using that is you then remember the api better for when you are programming again. I've done this before for simple jobs.
Isn't fiddler intended to be used to capture requests sent from already running apps and not to make standalone requests to APIs? Additionally it is not multi-platform as far as I know, you can only run it on Windows machines.
I've used Fiddler both for capturing existing requests as well as firing off my own to test an API :) You can create one from scratch or modify one that was previously captured (the latter being really handy for dealing with auth and large payloads).
Re xplat: they recently announced a cross-platform beta that will replace the Windows-only one in the long-term; I haven't tried it myself though.
I'm a big Insomnia fan and always recommend it over Postman as it's simple to use. Although even it feel a bit to "modern UI like" to me. I'd really love a old fashioned win 95 UI for this kind of thing. Tortoise git for example is my idea of a nice UI for a tool.