I've seen worse. WRT54G for starter. Or Cisco RV042 (some are Fast Ethernet, others are Gigabit).
The WRT54G was an other major milestone in wireless networking, the first reliable wonderful mix of a home router with 802.11g wireless, a 4 port switch and open source firmware. It survived long because there was for long nothing else but 802.11g for the home user. Yes similar to the RT-AC68, they used available new hardware to build the "same" router model for many years, and they even figured out the hard way that open source is a crucial selling argument (resulting in the WRT54GL).
Recently I noticed this for the WRT54GL:
No where the USB capabilities are listed, although the official marketing picture shows it

I doubt the WRT54GL you can still buy today has the same hardware as years ago, although Linksys makes one believe there is "only" a 1.0 and 1.1 hardware version.
New router models started to tumble into the market with 802.11n and even more with 802.11ac.
Router manufacturers simply follow hardware manufacturers.
Asus like all the competition have to release new router models with higher promissed speeds.
Deep in my heart I wish Asus would focus on one model, e.g. the RT-AC68 and develop that over time into the best most reliable router.
By the way, is the power switch in the RT-AC68 the same as in the RT-N66U, the one that fails over time? Or was there some enhancement at that end as well?