It can be done without an instructor and I am living proof of that. Never belonged to a club and probably never will.
I have my own personal liability policy and fly mostly in my backyard, but sometimes at local parks.
I don't like having to share airspace and I don't like the politics of groups so I've avoided the whole mess by staying on my own. I am fortunate to have forums like this one to teach me everything I need to know.
How did I learn on my own? Lots of reading and lots of crashing. Now I've gotten to the point where crashes usually only happen with some kind of mechanical or electrical issue, instead of pilot error, although I can still dumb thumb with the best of them.
Being on my own allows me to experiment, without having to deal with murmurs from the group about the possibly odd choices I might make. I do what I want. I really enjoy the solitude of it, and if I screw up, I don't have to deal with snide comments or backstabbing that will sometimes happen.
I miss out on the positives of a club, such as making new friends and getting face to face help or advice. But I have family and friends for social occasions. Model flying for me is a personal thing, not a party or group event. JMHO.