The "walking simulator" meme is just wrong and is a description levied by people who haven't actually played the game beyond the first few hours. Vehicles become available pretty early on and are a core component of the gameplay. Players even have a garage where they can store, manage, repair, charge, colorize and share various vehicles with other players online. A very significant part of the game involves the collective construction of roads in order to maximize travel efficiency using said vehicles. The game is certainly not without its issues, but "walking simulator" is just a thing people on the internet say to annoy fans of the game.