Bottom line: there is no right way to play dnd. Play what’s fun for you. But if you’re interested, 3.5e was very grounded in specific rules that allowed you to flesh out specific elements of the world and your characters. This allowed an incredibly detailed version of worlds and combat but gameplay could be painfully slow, especially for new or indecisive players. 4e was a very unique system that made a lot of changes from 3.5 that many found unpopular but was focused on cinematic and action-paced encounters designed to allow tabletop gaming to compete with computer gaming and MMOs. A lot of the elements of “danger” were removed. Dying took longer. Resurrection was easier. And every class had flashy moves to utilize. But it was a lot of change very fast and not handled as well as it could have been. 5e did a lot to marry those ideals. It gave more detail and allowed the game world to be as dangerous as the group wants it to be, but ultimately still less lethal than 3.5. It took a lot of the flashy cinematic class abilities that were fun from 4e. It’s also the current thing going. So all new source material will be in support of it. As a DM, 3.5 was my jam. It’s still my favorite. But I’m very writing oriented, so I love using fine detail for world and character flavor, and I like combat to be deadly. Play what you like though. The first rule is fun. So if your group is playing 4e and enjoying it, screw everyone else.