How much easier is it to Climb hills with Road bike than MTB?

I have an MTB which I bought about 9 or 10 years ago (was worth about £160 when  new- so it’s pretty crap compared to what the rest of you got)
Its 14.5kg ”light”, I have recently upgraded tyres to low rolling resistance schwalbe hurricanes and it made a really good difference as to how fast I can get it to roll+ I managed to shed 550grams just from upgrading the tyres 😀

I still like the bike very much ,it’s the perfect fit for me and all that,or I just haven’t tried anything else in my life so I don’t know what a better bike feels  😆  But when there are some incline, I just feel dead after a 1-2 minutes climbing one and have to do it standing up,sitting=no chance even on the lowest gear. + I sweat like crazy from climbing.

Now I’m just wondering if it’s my shit form/experience/stamina ( I’m 1.86m/ 77kg and fairly active so I can’t really complain about anything)
Or it’s just easier to do it with a better bike?
Or it’s the exactly same heavy work whatever bike you have?

Those who have tried/have more than 1 type of bike what’s the actual difference between each of these types of bikes when it comes to climbing up an incline?

-Crap cheapo 15kg mtb like mine
-Expensive 10kg Mtb
-Decent sub £1k 10kg Road/CX bike with good gears?

How would you describe the difference in feel/hard work between those 3 types of bikes?