Why am I not allowed to join my friend’s Minecraft world when I play on switch?

I play on a Switch, I bought Minecraft on my switch and Have a Microsoft account. I already tried to reset my switch and redo the wifi router. I don’t understand, I play Minecraft on a switch and my Friend plays on a playstation 5. Whenever I try to join his world it says “Unable to join world” and when I make a word so he can join me. He gets stuck on the loading screen. Something big is happening here to cause this problem.

:)