The fun of RPGs to me is the better I am at managing my characters and items and gear and guessing about dangers the longer my expedition can last before I have to go back and restock and save. Without random encounters there is no reason to be good at managing your gear and abilities or assessing the risks and rewards of different paths, instead you just easily dodge every enemy and collect every item to improve your gear as much as possible before the boss then decide if you need to farm weak enemies for xp to level up, the entire fun of the game is destroyed. Because you cant pretend that the enemies are a threat, anytime you are weakened you are not going to force yourself to fight a losing fight just to pretend the game still has stakes.
But you will never beat the game if you just run past enemies, the bosses require you to level up, and upgrade your gear. As for my self I don't feel like you need random battles, cause a lot of times when I'm ready to fight a boss, I don't want to fight a bunch of enemies that are just a waste of time.
Though dragon quest 3,4,5, and 8 are my favs. Most of the time some of the random battles were annoying, cause there weak monsters that I didn't need to fight, cause you get to a point were you only need to fight a boss, and you just use the spell, holy protection the whole time.
Also if you play with difficult settings on DQ11, you are not going to run past every monster, cause you won't beat any boss without grinding. If you want a challenge then just play DQ11 with every difficulty setting on.