One realization I had that has helped me progress on foot switches is to stop thinking about "how much weight is in each foot" and start thinking about "where is my center of gravity."
Let's assume you are doing the typical back foot forward, front foot backwards foot change (as opposed to a "jump and twist and land" style). The goal is to swap feet positions without changing your center of gravity, so that your foil doesn't change elevation. That means when your rear foot comes off the board, you are in an unstable static position -- your center of gravity is well behind your single point of contact with the board, so if you do nothing else you will fall backwards. That's actually the feeling you should aim for in that brief moment when there's no foot on the tail of the board. If you went to a stable static position after lifting your back foot, then your center of gravity would be over your front foot, and your foil would quickly nosedive. That is, in fact, what kept on happening to me for all of my early attempts!
So I knew I needed to keep my center of gravity static through the foot change, but I couldn't make it happen on the water. So I put my board on the living room carpet and practiced. If you do a slow, stable foot change on the carpet, you can feel how your weight moves from the center of the board, to the front, back to the center. And if your board has nose rocker on it, you can see that movement, too -- the board rocks forward then backward. If all you do is speed this motion up, you'll still get the rocking. My goal was to get my feet switched without seeing much or any rocking in the board. I realized that it's incredibly difficult to lift your back foot without moving your center of gravity forward first -- your entire life's worth of muscle memory has taught you how to keep your center of gravity INSIDE of your overall footprint so that you don't fall over! So to me, when I got it, it didn't feel like "lifting my foot without moving my center of gravity", it felt like lifting my back foot while putting FORWARD pressure on my front foot, like I was trying to take a small leap backwards. So that's what I visualized -- lift back foot while pushing front foot forward, and quickly bring back foot up to where front foot is, then send formerly-front foot backward to (literally) catch myself before I fall over. CAUTION: your board might slip around on the carpet with that front foot forward pressure, so try not to eat shit in the living room.
This drill helped me. But so did several other things I'd read. E.g. I employ the above advice about giving a quick kick to the tail right before switching, so that the board gets a little lift before you take that rear foot off. Because in reality, you probably aren't going to keep your center of gravity perfectly in place during a switch, so doing the tail kick compensates for the upcoming moment where your center of gravity is too far forward of the balance point. And the other very helpful advice was to just move your feet around on the board and realize that you can still find the balance point, regardless of where your feet are. Also do quick little lift-and-replace movements of your back foot, to get the feel for being on one foot briefly. These feel silly, and probably look even more silly, and they're surprisingly unnerving at first, but they're a good little drill.
Finally, #1 tip -- keep trying! It's easy to let yourself just keep riding around and doing all the stuff you already know how to do. It's harder to literally eat shit every 30 seconds, especially when there are boats and paddleboarders and sunbathers and all kinds of observers around. You feel dumb. But that's the only way to get better. Eat shit, and then think critically about why you just ate shit. How did you visualize things were going to go, how did they actually go, and what caused the discrepancy? Nothing wrong with just having a fun session doing the stuff you already know how to do, but if you want to learn new stuff, you gotta pay the price!