I have had a few mk1's as have friends back in the 80s/90s and when they were around 5-8 years old few suffered imo it was later years and milage, unless they had (real low miles and used stop start all the time with a fat barstuard owner). I think the later models with tinted glass helped matters. Were as the mk5's suffer earlier imo or ours did as did quite a few others from another forum i was on at the time in 05-09.
VW are like any company of today if they think they can save a penny here or there they will. They live off the image of quality they created with the mk2 golf. The same as Audi live off the image of the Quattro and the type 44 100.