As with all things, enter with your eyes open. Almost all of us have bought part-worn tyres at some point - when we bought a second hand car. You'll almost certainly have trusted your family to part-worns, in a minicab. If the driver in the video had bought brand new tyres, but continued to drive on cold wet roads when they were worn to 1.05mm, he'd still be in his current tragic situation.
I consider myself very fortunate to be able to afford a GTI, and to be able to buy good premium tyres. I'd buy a slower car and continue to buy premium tyres if money became tighter. However, if you're careful, it's possible to get a bargain with part-worns.
Caveat emptor.