Jiu Jitsu and wrestling are the most important part of mma. It's not even from the sense of actual submissions or finishing the fight. The reason it is so important is because if you are great at jiu jitsu and wrestling you can dictate where the fight takes place. If you want to keep it standing and you have the wrestling to prevent the takedown, and the jiu jitsu to navigate the ground movement to get back to your feet, you have the advantage. If you are fighting someone with strong standup, and you want to not only use your wrestling to get the fight to the ground, but jiu jitsu to keep the fight on the ground, you have the advantage.

Overall, you must be well rounded, but if you cannot dictate where you want the fight takes place, you are not able to stack the odds in your favor.

The only way to prove to someone that jiu jitsu is not hype is to get in there and grapple or spar with them. If you think it's hype before, you probably won't feel the same after.

As for the original intent for self-defense, it's great. It's also very applicable still for sport jiu jitsu and mma.