I love FF4, but I think at this point it's more historically important than anything. Random battles in general aren't always popular and it's very much a prototype for later JRPG design. The reason for encounters like that is FF4 was the first time Square made an RPG where the player character roles were set in stone. They felt they could make encounters more targeted towards a certain character class, or make them puzzly in general. I think it's mostly fine (the encounter design creates a contrast between going up and going down a certain mountain that I think is pretty cool), but it can also be kind of a disaster. Looking at you, Magnetic Cavern. It doesn't help that the 2D versions are among the easiest JRPGs ever made, so it's less of a challenge thing and more going through the motions.

FF6 is great for getting more of the party involved, though. One of my overall favorites in the genre.