The whole it isn’t fly fishing debates are pointless... fair enough if a style isn’t for you-
but “Czech nymphing isn’t fly fishing?
it’s only fly fishing if you use a flyline”...

So how about-
Traditional Czech nymph with only a couple feet of fly line out the tip, 8’ straight through level leader with a heavy nymph..... is it fly fishing???
What about a slightly lighter nymph???

What about a 6’ glass rod with 12” of fly line out the tip casting a 9’ leader and dry fly... is it fly fishing???
Change that dry fly for a lightly weighted nymph... is it fly fishing???

30’ Euro leader... no ‘fly line’ off the reel... casting a nymph... is it fly fishing???
Take the nymph off, still no ‘fly line’ off the reel but casting a dry.... is it fly fishing??

It’s all fly fishing