I also used to be an annual passholder, hadn't been in about 3 years and recently got an annual pass again, but my experience is very different. I've been following this forum for the last few years and because of all the negativity had a very low impression of FastPass+ and the parks. We got passes in August and I wasn't sure I was going to like it again, but we have already been 14 times since then and are loving it. We went to Food and Wine concerts several times (it was perfect to get FastPasses for concerts ahead of time so we had guaranteed seats) and love going to the lights at Hollywood Studios, looking at Christmas decorations in the resorts and listening to the storytellers at Epcot. We often just go for a half day or an evening for something specific like that.
We are finding FastPass+ quite handy and are often able to get what we want a few days in advance. The app works great and has never crashed for me. It is very fast, WiFi is now good throughout the park (it wasn't 3 years ago when we stopped going) and I like using the app to make reservations and look up wait times.
We regularly plan a trip based on what FastPasses we can get. The good ones like Toy Story and Seven Dwarfs Mine are often gone, like you said, but sometimes we can get them and then we plan a trip around it. I find it reasonable that people who pay a lot of money to stay at the Grand Floridian can get a FastPass for Seven Dwarfs more easily than someone like me who can go whenever I want, but I can still ride it quite often. A few days ago we were at MK and at 4pm were able to change a FastPass from Pirates to Seven Dwarfs. I find that we can more often get these good ones late as I suspect people are canceling them or more are opening up.
I like that the 3 FastPasses you get are often pretty close together, like all in the morning or evening. They are usually within a 4 or 5 hour period so we can go for just a half day or still visit another park. I think it's great. The Magic Bands work so well to get in the park and scan for a ride. When I think back to the old paper FastPass system and how CMs had to check times manually it seems archaic. Last time I was at Universal there was a huge line to get in as many people were having a problem scanning their ticket. Now at Disney there is almost never a line and you just scan your Magic Band, the thing turns green and you're in. I think it's brilliant.