sorry if this is obvious or has been answered. I tried looking around and didn't see it. Also I'm getting around Magento okay but by no means an expert.
I have a Magento 2 theme that it was recommended I purchase for work. I have created my own theme that extended that purchased theme and it works and seems properly set up.
I then tried to create less files to extend the styling but none of them worked. I did all the necessary steps and my changes just never showed up. Finally I found that the issue was that the purchased theme does NOT extend Magento Blank or Luma. It's a top level theme. None of the basic extending mechanisms (_extend.less, _widgets.less etc) work. When I updated the theme table to have the custom theme extend Magento/blank, my css changes do appear but then the theme itself is a bit wrecked, presumably because it's including a bunch of Magento stuff that it hadn't before.
So, I don't know where to go from here. First of all, does that diagnosis sound right? It's completely possible that there's some way to do it after all that I haven't thought of. Then, is this normal? Should a purchased theme extend Blank? (and really the question is, if I dropped it and purchased another will I have the same problem).
How can I make my own style changes to this purchased theme? Or should I abandon it and start over?