Big ask, but other VTT's either have poor quality features, image quality, never fix bugs or update wanted features, or are stuck behind some significant paywalls. I'm a pro member, and know people need to be paid, so that's not the issue. Inkarnate already has the best map making (imo) it would be a no brainer to use the maps created here on the same site if it were also a VTT. I'd rather pay for another form of subscription here where I can trust that the art and features are quality and the community is heard and actively responded to than begrudgingly use a free, let alone paid option that does nothing but stress me and my players out.
I could see how using Inkarnate made maps on an Inkarnate VTT would potentially allow for better in real time customization of maps during gameplay like adding and removing assets, depicting the change of lighting, adding filters, adding/editing text, etc. Hiding layers of environments and pathways and revealing them either by toggling the eye icon or for example in the map uploaded here, if I were to remove the roof asset to reveal the upper level.
Example of trying to use a map on a VTT site that lowered the quality, compared to the actual quality from the Inkarnate map.
(Credit: I cloned and edited a Mati map)