I have a MacBook Pro 17" (late 2011), and if the Geekbench benchmark points are to be believed, my 5-year-old laptop is still very much a viable option to last year's model (MPB 2015), and quite possibly even the new MBP 2016.
http://browser.primatelabs.com/mac-benchmarks
I have replaced the original hard drive with an SSD drive of 1TB, and also switched the DVD drive to a 1TB hard drive, so I have 2 terabytes of hard disk space. The price of a 2TB IDE SSD is +1200 € on top of the base price of the new MBP. 16 Gigs of RAM also seems quite unbelievable, considering that's the maximum on my 2011 MBP. The speedy SSD on the new model might make up for the low RAM capacity, though.
I play quite a lot of games on my MBP, so a dedicated GPU is a must. Choosing the best GPU, 16 gigs of RAM and 2TB of storage, the 15" MacBook Pro 2016 costs 5099 euros. My current laptop cost about 3000 euros 5 years ago. And in some ways, it's still better than the latest model (more ports, bigger screen, interchangeable parts).
In five years, Apple has failed to design a computer that I would actually want to buy.
The trouble is, I love MacOS, and that's really the only reason I haven't switched back to a PC.
I haven't had any trouble carrying my 17" around.
I don't need a lighter laptop. Just the same size with
more processing power, upgradability and a retina display. That's not too much asked, now is it?