What's the obsession with the down being the only "fun" bit?

The modern mountain bike was designed to be able to ride up the mountain and come flying down. Something you cannot do on a road bike or cyclocross/love child bike.

depends, some modern mtbs are designed to get as fast as possible from a to b cross country and as you spend longer climbing than you can decending, a bike that climbs faster will get you from a to b quicker.

depends, some modern mtbs are designed to get as fast as possible from a to b cross country and as you spend longer climbing than you can decending, a bike that climbs faster will get you from a to b quicker.

Yes, but you can still hammer downhill in a way that would kill a road or cyclocross bike.

‘You’re not real cyclists until you’ve coughed up a lung on Buttertubs’

That takes me back. I remember reaching the top only for two young ladies wearing wetsuits to suddenly appear from nowhere. I thought I was hallucinating from lack of oxygen, but it turned out they were cavers and had just emerged from a sink hole.
I did a bit of off-roading round there on a CX bike in the 80’s – Malham Tarn, Goredale Scar and so on. The point was to get off the beaten track, not set speed records downhill.
And yes, I am an old duffer!