I've used MacOS for about 15 years now, and I almost _never_ use full-screen [1]. What I do instead is group windows in the different desktops by task / context. These windows are mostly sized to take ~80-90% of the screen, but I make them all different sizes and slightly offset from each other. That way I can switch from one another by clicking on the small sliver that peeks out from behind the current foreground window. That type of context-switching is a bit more rare; the most-used action is the 3-finger swipe / ctrl-arrow.

One thing I miss from Leopard is the ability to put your spaces into a grid instead of a line; made for a bit more efficient switching between them.

[1]: The only exception which is pretty much always full-screen is my terminal. I use tmux for multitasking in that "space".

I've been using a Mac full time for a little over a year. I'd agree fully with you on the full screen going to a separate desktop. Extremely annoying.

However, you can switch desktops with control + right/left arrow. No need for the trackpad.

Because I'm easily distracted, I frequently have all major applications maximized. That's how I always used Windows. Fortunately, I can have the same on the Mac. Maximized with the dock showing below and all apps on the same desktop. Full screen is a rarity for me.