I think what most people gloss over when talking about open world games is that they all have 3 or 4 pillars to stand on, which are traversal, interactivity, beauty and combat. Even if one of those pillars is not good enough, having another one of these 3 be AMAZING will make it so people don't notice the weak link as much. Spider-Man is a good example of this. The open world in beautiful, but the interactivity level is not that high or complex compared to something like GTA, and there's not a lot of variety in the things you do. The way you move around the city and the combat are the things that elevate that game and make it much easier to forgive the parts of the game that didn't get as much love.
Dragon's Dogma is also an example of this, and that is a game I also love. The combat just carries that game hard and makes me forgive a LOT that could've been done better.
By that metric, the worst open world in videogames, specifically for a high budget title, would have to be Final Fantasy XV, and I LOVE Final Fantasy. Few times have I ever been so disappointed by something. The world is not terribly interesting or beautiful compared to what we were promised, the levels of interaction with the world are non-existent besides fishing, combat is pressing circle to win and traversal is one of the worst in any open world game. Driving that car felt like driving a bathtub on-rails. It truly feels like a game that is fighting itself about what it wants to be.