I've never got the Holga thing, in so far as why people would spend £50+ on a new chunk of plastic when there are so many interesting vintage box type cameras around in full working order for less than £10? Many of them will give similar (or perhaps even more unique and pleasing effects) and you could buy five or six of those classic cameras for the price of a new plastic Holga. Plus, you aren't encouraging the production of yet more plastic to be recycled or put into landfill in a few years time when the camera breaks.
As for the results, the artistic 'skill' comes in learning the effects that the camera will give in various lighting conditions, then matching that specific effect to suit a particular subject or scene. However, it seems not all Holga users have grasped this concept, and some just trot out a series of blurry, underexposed images that just have a 'Holga' look to them, but don't actually add anything to the often rather mundane image being presented as an 'arty' photo.
Instead of people thinking 'now why do I like that photo', it seems they just see it's been taken with a Holga and think buying one will make any photos they take with it look like that. It's not that simple! It's a bit like Les Dawson's famous comedic piano playing, you've got to play very well to play that badly.
Each to their own though, and if using a Holga gives people pleasure then who is anyone else to criticise this or say it's wrong? One of my photography hobbies as a young teenager was buying cheap box type cameras and mock TLRs from jumble sales and junk shops then putting some film through them to see what I could get out of them. Some of the results:
1924 Kodak Brownie Box Camera on Kodak Ektachrome 100 taken around 1979.
Coronet Twelve-20 TLR box camera (which produces a halo effect when shot into the sun using the sliding smaller aperture) on Ektachrome 100 taken around 1979.
And matching the 'look' of the camera to the scene, one from that 1924 Kodak Brownie again, taken on a dull day in 2017 on Fuji Acros 100.
That's the thing with using old cameras, 'weaknesses' can be used as strengths; shooting this triplet lensed 1964 Yashica 635 TLR wide open gives lots of swirly bokeh, which lends a time-tunnel type effect to the background of this photo of a steam punk.
So that's why I don't really understand the Holga thing, as lots of fun can be had exploring 'vintage' budget alternatives (not that a Yashica TLR is a budget camera, that was only included to illustrate a point). However, that's just me and the opinion and thinking of others will vary.