Yoshi is probably one of the weirdest and stupidest characters to fight in the game. He's completely horizonally and vertically defensive. You won't have much luck coming in directly from above or from the side. Never pressure his shield from the side, pressure it from above.
That said, moves that really aren't good against yoshi for spacing include peach's dtilt, f tilt, Bair, and f smash. Her tilts are punishable by grabs because of yoshi's running speed, Bair is easily pivot grabbed and F smash has enough lag where yoshi can grab you at the end.
Peach and yoshi is an even dumber matchup to play, albeit fun. Your main goal is to hit him in his blindspot (his nose), which peach is quite good at doing. You also have to avoid his grabs and egg tosses while doing this. Yoshi outcamps peach at long distances, Peach outcamps yoshi at middle distances. Nair OoS ***** his Bair approach.
Dealing with eggs is annoying, you have to learn to Powershield them. Yoshi can use them from the ledge and use them while minorly sliding. They should only post a thread if you're in the air or floating. I try my best to float out of their range. Spacing Fair on yoshi is also extremely unusual. You have to space it just right to hit his nose but to make sure it's above his tongue range so he can't pivot grab you.
Once you learn all these things there are pretty much three moves that you really need to look out for: Up smash, grabs, and Egg lay. Egg lay is annoying as **** if the yoshi uses it well, that's why I'm always Fairing against yoshi. He can use double jump cancel with (his b moves cancel double jump) and basically weave in past your defenses and catch you. With Fair you will either knock him away or deal 15% or so (and since with egg lay he can only do like 13% it's worth it). The most annoying thing about egg lay is the bad position it puts you in. You don't wanna be high in the air against yoshi., that's how he kills.
I'll think of more later, I'm kind've pressed for time atm. Learning his recovery patterns is amazing for reads