There seem to be a couple of things going on with this thread. There can definitely be a bit of a "joyless" approach taken by some experienced players towards people starting out that says that you'll only get decent after years of rigourous technique and lessons (I haven't heard anybody on Basschat take this approach btw). And then are other people who think that you should get a bass and just start playing and having fun. The two are not mutually exclusive, and as somebody who is self-taught (in the sense of having virtually no in-person lessons) I definitely think that just playing is possible. However, bad technique on DB more than most instruments can definitely hold you back - both in terms of causing pain/injury, but also (as @neilp points out above) in terms of playing in tune.
I'm not as good a player as I'd be if I'd adopted a more consistent/rigorous approach to playing and practicing, and I've had several points where I've had to re-learn and ditch bad habits (particularly after watching better players than myself in person or online). But I've always enjoyed the journey and so I guess what I'm saying is that DB is both fun AND challenging at the same time, but it's definitely worth paying attention to getting some of the basics right when it comes to technique. And there are people here on Basschat that can definitely help with this....