See, I hear all the time how easy Foundry is. And then you look a little deeper and you find dozens of comments like this.
I agree Fantasy Grounds is complicated and hard to learn. But we're talking a few days. not a few months.
My experience with FG (which was around 5 years ago, just before FGU came out) was that it is complicated in a different way and to different people. With Foundry, the difficult part is for the GM, and it's mostly technical. Setting up modules, customising systems and debugging takes time. But once you get past that hurdle (or don't try to automate everything and thus don't need that much tinkering), I think actually setting up and running your game is incredibly easy.
With Fantasy Grounds, I never was a GM, but our GM (who was running a prewritten module) always had trouble with how unintuitive the UI was for running the game. And the players likewise never fully understood how to do the most basic actions. How do you select a token? How do you change scenes? How do you add new stuff to your sheet? All of these kept being problems 10+ games in. Once that GM switched to Foundry and basically imported the FG module to her Foundry world with a paid plug in, everything was butter smooth.
Another downside for FG is the pricing scheme, especially if you're trying to run a game from the global south. With Foundry, only the GM needs to pay (and despite what everyone says, you can set your game up for Internet access easily with stuff like Hamachi, which was the default way to run LAN parties 5-10 years ago), and people just connect with their browsers. With FG, either the GM pays for the much more expensive ultimate license to let people connect with the demo, or everyone buys a license. That's a big hurdle in countries where the minimum wage is 300-400 dollars!
But I can honestly see how FG can be a preferable VTT for some people. You can pay for the books and have everything set up for you. And if the interface becomes intuitive to you through habit, then it basically has no downsides. But that's kind of like saying Crusader Kings 3 is super intuitive and fun to play after 100+ hours. It's a great game, but I wouldn't recommend it to people who aren't ready to go through its learning curve.