I have a question, maybe some of you know....Why don't any of these VTT look and operate like say, old school Baldur's Gate? They seem to want to go that direction, with animations and rendered sfx.
There have been plenty of in-house attempts at Isometric VTT's ... but they are inherently limiting. Spell animations that are in the can are easy to add to 2d. And there is a workaround for animated 2d sprites leveraging World of Warcraft's 16 years of digital art for private use. (WoW is the singe largest source of digital animated fantasy artwork on the planet, so that matters). But again - it's 2d captures from 3d assets and is easy enough anybody can do it.
The vast majority of us are simply not capable digital artists. Many of us who are well experienced with VTTs ARE capable "modders" and outright image thieves. We grab images off of Google - or from within stripped PDFs -- routinely to illustrate our games with maps and character art. That's the raw fuel behind VTTs.
And if we are running modules,( without regard to the system), we have ready access to that 2d art. The maps for the adventure are presented in 2d. That is so whether it is Old Skool TSR Blue+White blueprint style maps, or the latest shaded illustrated map from Mike Schley, Rob Lazzaretti, or whoever it may be.
We also have lots of 2d top-down images to use that are created from a vast number of map artists on Patreon, too. That includes innovative animated maps on mp4 from Dynamic Dungeons, as well.
In short, the ability for GMs to lift and use assets from the games they want to run, based upon the adventures written for those games, is virtually all in 2d form. While isometric is a 3/4 view cheat on 2d drawings, they are not easy assets to find or to make. So that tends to be a huge hurdle that gets in the way; it doesn't make it easier for GMs to make their own adventures or repurpose an existing adventure they have access to in their VTT.
Going back to NeverwinterNights, BioWare's version of the game sold well and its community had HUGE community support and participation. While it took skill to develop a module overall, the tilesets and toolset for NWN1 were relatively easy to use. Even the LEad Developer's Grandmother could screw around in the toolset and make a map in 15 minutes (this was, literally, BioWare's design goal for their toolset - known as the "Trent's Grandmother test") When Obsidian released NWN2 that was based on a more advanced terrain mesh system, the number of community modules
dropped like a rock, to a 1/50th of what had been released just the year before. What that change in building terrains and the NWN2 toolset did was that while it made something that was professionally done look better, it raised the technical bar to participating in module creation by an Order of magnitude to reach that level. Otherwise? It looked like shite. Trent's Grandmother gave up after 15 minutes. She might be able to make a puddle of water with, but that was it.
And that's what isometric VTTs would do: raise the bar to technical participation by most people by an Order of magnitude. For those who could get over it? It would be cool, sure. But that's a tiny fraction of those creating adventures to run on their own VTT's now.
Hell, most DMs and GMs who use Roll20 complain about the work it takes to set up those advantures. Can you imagine the kvetching about an ISO style VTT? Yikes.
There is a reason that a battlemapping program with a lot of features that is still easy to use like DungeonDraft has moved the needle so fast and so far so quickly: because it's accessible. Isometric VTTs would not be. accessible.
3D VTTs? Those are even worse in terms of the technical barriers they would create to using freely available repurposed art for use in your private game. If you want to learn 3d Modelling and texturing? Sure. Knock your socks off.
It's just not practical for the other 99%.