The combat would be a lot more realistic and since Fractured seems to include a lot of adventuring, it would be cooler to look across landscapes and regions to really take in the beauty of the worlds.
The problem here is that you can't easily change a game with an isometric perspective into one with First/Third Person Perspective. There are numerous differences between the two which make going from isometric to FPP a huge step up in cost.
- In isometric perspective, all characters are tiny and seen only from a certain angle. This means their models can be of relatively low quality (small texture resolution, low polygon count), and their animations will be exaggerated to look clearer from that angle. While in modern game development pipeline upscaling a model might not necessarily be a problem if you're always starting from a way-too-high-detail-to-put-into-actual-game model, redoing all animations is going to be work-intense whatever you do.
- There is no sky in isometric worlds, which means now you have to make one.
- There is no horizon in isometric worlds: you only need to render a tiny parcel of land where only a handful of things can fit. When you suddenly add a horizon, there might be loads and loads of thing that a player is supposed to be seeing, and while you never have to actually render all of them, you now have to worry about when and what to draw, which is hard and can lead to numerous problems ranging from being too lenient and melting an average graphic card, to being to strict and having pop-in (things suddenly appearing out of thin air that should have been visible from further away; things too abruptly changing from distant&low-poly to close&high-poly).
...I'm a terrible writer, but you get the gist, yes? It would be much more harder on the dev team, therefore the game would either require a much higher budget, and/or would have much smaller scope, and/or would make people say "hey, 2008 called and they want their graphics back".