Latex pillow. They do NOT lose shape/consistency at all. Trust me, I bought a latex pillow and I pretty much always use the latex pillow now. I use the larger memory foam pillow when I want a harder/thicker pillow, but otherwise I prefer the latex pillow since I don’t have to worry about constantly fluffing it up or anything. I still flip it around sometimes to get to the cold side of course, but not as much for other pillows. Some people want “ergonomically-shaped” pillows, which have a bump for neck/spine support, and those kinds of latex pillows exist too.
A lot of people swear by millet pillows and buckwheat pillows (and other hull-filled/non-synthetic pillows) too. What I can say about them is they’re firm and heavy (buckwheat pillows are harder and millet pillows are softer), they stay cold, they have a strong smell, and they whisper statistics into your ear when you’re trying to sleep (they’re very noisy, especially ones using a less soft/less stretchy fabric like canvas or sateen). They’re probably better if you want more neck support. People like PineTales pillows, especially side-sleepers (I’ve never tried them though).
The best praise I’ve seen a pillow brand get though is Purple pillows, again from side-sleepers, but they’re $100-200 and I haven’t tried one. I don’t particularly want to finance a pillow.
Every time I have to use a typical pillow I’m like “wow this fucking sucks” and I have to fiddle with the pillow constantly because it loses its shape/firmness after a few minutes and stops feeling comfortable. Not something that happens with good latex pillows, and it’s less of a problem with memory foam & hull-filled pillows than in other pillows.