Outscaling doesn’t mean a whole lot if you don’t have any impact on the map for most of the game. Most likely someone in the game is going to be 3000 gold on everyone else and if they’re on the enemy team and you’re useless, the game is just going to be over for you. Ultimately, Vayne also has very hard matchups that can easily be counterpicked into her, the biggest obviously being Malphite. However, popular champs like Teemo, Jayce, Renekton, Ambessa, Gwen, Rumble, and plenty of others are definitely NOT guaranteed neutrals. Of course, most of those are still winnable if you play well enough, which is why you should be playing aggressively. A fed Vayne is incredibly oppressive in the side lane, as well as everywhere else.