I never know how to answer "how hard is...?" type questions. I began learning in the 1970s and I found it as hard as I expected it to be. It.took me several months even to be able to tune the guitar. I'd say I'd been learning for a couple of years before I could have claimed to be able to "play the guitar" at all. That's what I expected though and knew it would be several years before I'd be a reasonable player. I found learning frustrating at times, difficult and time-consuming but I loved every part of it. I got a LOT of satisfaction from being able to read a simple tune from the music, being able to play a scale, being able to play a few chords etc. etc.
I began learning compeletly from books. I would say I learnt "properly" - none of the important parts were missed out and nothing was dumbed down. I am no great player but I've held my own in a few bands, written my own material and recorded covers for my own enjoyment. I can easily play as well as I need to enjoy myself and do what I want to do.
But, LEARNING FROM A GOOD TEACHER WOULD HAVE BEEN A LOT BETTER. Nowadays, things are, in my opinion, harder. There is simply too much information and too many "experts". The vast majority of stuff I've found on You Tube meant for beginers is absolute rubbish; things that will hinder rather than help. There are a lot of really, really confused "players" out there. People who have learnt really advanced techniques but can't play a barre chord or a basic major scale. A lot of people seem to learn bits and pieces at random, from the internet, and then wonder why they still can't play.
I agree with Tommy about JustinGuitar - he's a great player and a good teacher. Personally though, I have problems with this sort of stuff. I watched one of Justin's "lessons" on playing (I think) a D chord, and it went on, and on, and on. What he said was correct and I couldn't have done any better but a few sentences on a page followed by a standard chord diagram would have been much better. I'd far rather learn from books!
The thing is, no one on the internet can see what you are doing. Explaining something once and then moving on won't work for most people - they need to have it explained to them several times and see what they are supposed to be doing over and over again. These videos tend to move at the pace of the slowest learner. For some people of course, they watch a video on, for example, playing a D chord, do what they're told and think they have it covered and move on. They've watched all the "lessons" but still can't play. When I learnt, turning over a few pages was far easier that loading and watching lots of videos.
That's my rant over - sorry!