No it's not.
It's still a good idea to pick up for the slight pp boost on farm maps (which aren't hard to play on HD), getting better scores / higher rankings and if you ever play tournaments you might need it there, too.
Don't forget that in order to learn Hidden you don't need to go full HD, just playing it regularly is sufficient enough to get really good at it. So just balance your plays out between HD and nomod (You can forget about HD on low ARs if you want, almost noone can / wants to play that.)
So yeah, it's a good idea to pick up. Just don't fall into the trap of thinking that you HAVE to have HD active at all time. Again, just using it every day for a few maps will make you really, really good at it in a relatively short amount of time.
Most people, and probably you, too, hate HD because it has a frustrating entry level, but once you get past it, you'll start liking it. Just don't start liking it too much, you want to be able to play all mods eventually and not become some OTP that will eventually hit a wall. (Maybe make an exception for FL and EZ, though)
You only have to invest a couple of dozen hours into HD to get to the phase where you're not hopelessly lost on it, and only a couple more until you're on par with your nomod skills for everything AR9 and above.
Trust me, the hardest part of any mod really is to overcome that frustrating entry level phase, and after that you'll feel really good about sticking through. Everyone went through it when they learned HD, and if you ever plan on playing HR / HDHR, it will definitely not be the last frustrating phase you'll have to go through.
TL;DR
Yes, pick it up. Play it a everyday, or make one day HD and one day nomod, whatever you like, just keep exposing yourself to them so you'll eventually become pro at both.
