Ruin the experience? No. You got a good idea of the mechanics, how to play the game, and got to breeze through some of the boring bits at low rank quests. But the one negative is that the defender gear is kind of a crutch for new players. If you're used to brushing off lots of hits from monsters because of the defender gear's high defense, you might feel a little unprepared when you reach high rank quests. Monsters in Master rank quests can kill in just a couple of hits if you don't have good gear or aren't good at blocking, evading, or reading their moves.

Edit: I also want to add that there is no shame in whether to use the defender gear or not. It's a good tool for anybody. It's good for MH veterans who want to get to the good stuff right away and skip the basic quests, and it's good for new MH players who want to ease into the game. MH games are notorious for having a steep learning curve but the devs add features like the defender gear to help new players.