Why can’t they just make a normal lord of the rings movie?

Because they already did? They did three. And they were so brilliant and are so beloved today that to attempt to remake them any time soon would be the height of folly.

A Hunt of Gollum movie isn’t exactly the #1 choice for a story set in Tolkien’s Legendarium that I would choose to be adapted. But of the stories that they have the rights to tell, it’s a fairly interesting premise. It’s not really likely to be a Gollum movie anyway. Aragorn is likely to be the protagonist.