Cheap electronics simply didn't exist 30 years ago, that's the difference. I own a 38 year old Marantz stereo receiver that will run circles around most modern big-box store receivers in terms of sound and build quality, I thought this was proof that quality has degraded over time until I researched the original cost of the unit. The receiver was positioned at the lower-mid range of the Marantz lineup at the time; it cost $450 in 1974 dollars which is about $2025 in 2012 dollars! You can buy a serious, near audiophile level piece gear for two grand that would put the old Marantz to shame (as much as I love it).
A $30 wireless router is an amazing piece of technology in its own right and really can't be compared to anything produced 30-40 years ago. I have Cisco routers that have been running 24x7 for the last 10 years and work perfectly, granted they cost 100x more than a Netgear with basically the same capability. As always you get what you pay for.