I think the biggest issue with a B5 remake is related to where the original show's strengths were. By todays standards, and even that days standards, most of Babylon 5 was subpar, the sets, FX, casting, etc, were mostly B level. The reason I once loved Babylon 5 and so many others did, was really about one thing. The longer form storytelling that remained on a coherent trajectory for 4 years. It was a series that felt more like a good book than most of the others, and kind of pioneered telling longer and more sophisticated sci fi stories on television. It really was groundbreaking in it's way.
Here's the problem, original episodes were at about 700k per episode budget. To bring it back today, and make it competitive in a space 20x as crowded as the one the original faced. (I think when B5 originally aired, there were about 3 sci fi shows in existence, now that number is probably around 60) the budget would need to be maybe 5 million minimum per episode. That's a half price sci fi show, competing against many double budget shows in the same space. Since, like GOT, Babylon 5 relies on the quality of it's long form story developments, you're talking about running it for 2-3 years before it can really shine. In fact, with GOT, the showrunners knew they would be cancelled if they only got one season, so they demanded a minimum of two up front. So let's say B5 needs 2 seasons at 12 episodes to really get back on it's feet. That's 120 million dollars, at minimum budget for a second tier sci fi show. That's a big bet on a horse that hasn't run a race in 30 years. I'd say financial backers are skeptical, but that's just a guess.
Zoom out a bit, and look at it in context, they rebooted Star Wars, the most popular sci fi franchise in history, then spent 20 million an episode, The Mandalorian, The Book of Boba Fett, Obi-Wan Kenobi, and Andor. All series in total amount to 49 episodes across six seasons of television. They seem to be having difficulty getting people to watch THAT.
So rising costs, Market saturation and fragmentation, an aging IP that didn't hold it's ground as well as some others. Sadly, this proposed reboot has a lot of things going against it, from a business/financial perspective.
I'm not saying it could never happen. Like all TV shows, they are one brilliantly charismatic and imaginative writer/lead actor combo away from success. J Micheal's writing was legendary, so I do hope he finds a way back into the system.