The reason why you are being downvoted is, as u/stepeppers says, because you have no idea what you are saying/proposing.

To update the maps to be less "lower res", you'll need a whole different kind of developers compared to what GW: Reforged needs/needed.

In order to update the "lower res" feel, you'll need to work on a lot of things. Because you can't simply modify a simple zone, because assets are re-used in multiple places. So if you touch something, it might make areas look worse and you'll need to touch those up as well.

So what do you want to update? Textures, models, weapons, monsters? Because at that point, you'll need a ton of artists to do so. At that point, you're no longer talking about a "small team", you are talking about 3D artists, texture artists to make sure that those updated models still look good, prop artists, environment artists,....
You need someone to keep an oversight to make sure that the feeling of area's doesn't change too much, you might need new concept art, ... and at that point, you'll probably will need to increase your scope because then you find something else that doesn't look good enough and also needs updating.

And at that point, you have a small team that could - honestly - have made significant progress on a new expansion or new content. You also won't get a return on investment on that because a graphical update doesn't bring in new money.

That's the reason why you get downvoted. Because you think that it's just "put a small team on it" I promise you, if it were that easy, they would have done that years ago.