Well there's a lot of people who came into the hobby with 5e, struggled through learning that one system reasonably well, and just don't want to learn a new system (not unreasonable, people have lives and varying interest in learning ttrpg rules). I doubt many of them would personally know or care about Traveller, but I think the market for this is people who play with these sorts of people and want to provide a version of Traveller they'll play, along with 5e DMs who like Traveller but don't personally feel comfortable trying to run it. It is a little funny, since 5e is sort of the compromise, makes-nobody-completely-happy system, to make compromise systems between it and other games. Meta compromise!
There might also be some market for people who just want more extensive 5e D&D in space rules than 5e Spelljammer offered.
But as someone who really loves 2014 5e (and really tolerates 2024 5e) I have to say I don't think it should be grafted into every situation possible. It's a pretty robust system, but if has never handled added subsystems well, and if your using it in a context where the core classes don't make sense well then you're designing new classes and almost certainly not playtesting them as much as is really required to do them right. And also at that point nobody's advanced knowledge of 5e really translates anymore and it's just a bait and switch.