While Mario has the location aspect and a long series of games (Mario Kart, Mario Tennis, Mario Party, Luigi's Mansion, Captain Toad, Paper Mario, Dr Mario, etc) that Universal could easily exploit by adding a resort to the Land and have the spinoff games being a part of but I don't think they will do that which leaves the main plans we have seen. Yoshi, Mario Kart, DK, and playgrounds. Essentially what we are getting is a real world dungeon crawl with a racing ride and a coaster which fits the main games. If Mario Party and that other stuff was being included and part of the land, I would argue it a much larger draw but in detail this is why I see Pokémon being a much better theme park land and advertisement.
You are right. Pokémon does lack a sole iconic location. However, everything about Pokémon fits levels of interactivity that Mario attractions being advertised do not. I think you missed a lot of hype that 20th anniversary Pokémon Commercial at the super bowl got. You had some many other things to do in the Pokémon games than just battle, you have the Team Rocket Game Arcade where you essentially gambled to win points to buy TMs or Pokémon back in Pokémon Red, Blue, Yellow. You had dungeon crawling elements where you can just explore and search away for things while using your Pokémon to help whether it was them using their strength or using their eyes to conduct Flash etc. You can groom and feed your Pokémon in the recent games. You had the safari zone which focus was solely capturing Pokémon and not battling. There was the Poke contests where you demonstrate how cool, cute, etc your Pokémon was. You have Pokémon snap and the Poke Camera thing in Sun and Moon where you take pictures of Pokémon and post them. You can make Poke blocks for your Pokémon, buy Poke beans, etc. You could solve puzzles and crimes at the fun house and in Detective Pikachu. You could just go exploring and walk around with no consequences at all. While Mario games are more linear, Pokémon was a bit more open allowing you the player to dictate what you did.
There is a level of world building, immersion, and experiences in Pokémon that crosses way more generational gaps than Mario. The only way and the only reason I see Mario being larger is I foresee is UC lacking the imagination or having creatives who actually have played every single game, seen every season, seen every movie, etc to actually hit that level of immersion that Potter has reached. A well built Pokémon land would be as relaxing or adventurous as the people there should want it to be. It shouldn't be limited to land but water, air, etc.