I know this first hand, building a developer tool startup and failing to reach any level of revenue. In the end, the tech was bought out by a larger company to recover a fraction of our VC investment.
The challenge is that when you're building software for developers, they already know how it must work.
It's like trying to sell magic tricks to magicians. Sell magic to regular people, and you'll see some significant revenue.
I've used Kite before. It was ok. But I am a SWE. It's entirely possible that Kite would have seen major adoption if the push was towards non-technical folks trying to get their feet wet in software. Eg: Data scientists or business.
The reason why BI tools sell so well at the moment is that you have tons of C-level execs that like the appeal of a business-optimizing tool requiring little to none of any actual software development.
Let that be a lesson to everyone. You can't blow away developers. They're just too damn ~~smart~~ well-informed.
Edit: Another anecdote: A buddy of mine built a bespoke OCR and document indexing/search tool. He has ~60 paying clients (almost exclusively law-firms and banks) that primarily work with printed pages on paper. No Saas. No free tier. The client data resides on an on-premise Windows box, avoiding issues with sensitive data in the cloud etc.
He's a solo dev with support contracts and nets something like $1000/month from each client.
For your average lawyer/paralegal, the ability to locate and reference a single page from thousands of pages in under a second is magic. So they pay for it wholeheartedly.