When 26" was it we were told we needed a 29".
When 29" was it we were told we needed a 27.5"
Now that you NEED a 27.5", it's about time the 26" comes back.....

Or monster gravel, or skinny fat tire, or carbon 26, or ......

Nothing wrong with trying new things for new experiences, but updates in technology make for the difference, not really wheel size. Curved top tubes, aluminum then cf frames, shifting, brakes and other tech had much more to do with mountain bikes getting better rather than wheel size.

Good luck with your search.