They were just trying to sound cool. This happens in almost ANY case where a player thinks they can just give one tip and suddenly anyone can beat a character.
In other words, no, Yoshi is not easily gimp'd. Eggs protect, double jump has armor, etc.
If you want actual tips against yoshi, well, I'll say that Yoshi's struggle in creating situations where a grounded player who's dishing out projectiles is at a disadvantage. It tends to come down to 50/50s in that situation, because Yoshi can't DA or Grab. Running in with Shield is slow, which leaves you with aerials and neutral B. This brings a 50/50 of:
Is your opponent going to shield your aerial?
Are they going to counter the tongue grab?
Which can be frustrating for some players. With WFT, try charging SS at any point (neutral B) to load up on pressure. This will make Yoshi not want to approach with a Neutral B, which you can then resort to playing highly defensively until they crack.
Dealing with FAir is a weird one, because it does have a somewhat specific hitbox. Basically, if a Yoshi is camping with FAirs, NAirs, and DAirs, don't approach. Try baiting eggs, then get in their face. It'll force them to switch up styles really quickly.
Just random tips and stuff, won't work on all Yoshi players, however, it's mainly a list of things that can get into my head when playing.