Which are best most secure routers? Vendors that accordingly issue, release quick security firmware updates after huge CVE, vulnerabilities discovered in their hardware are exposed publicly.
I have a Technicolor Modem,
I am not a techie,
but it is pretty good so far,
my ISP STOFA
is very good at updating Firmware as soon as it becomes available.
I use Torguard(big package with add-ons,
so I can watch US Netflix and be secure online)
Indian model DSL-2750U, D-link (Indian) just upload new 'rogue' 'arrogant' firmwares on site as recommended to update, with absolutely no explanation, changes, less features, as well as very buggy, my $40 Router above model got entirely ruined by updating firmware as they suggest 2 years ago.
In other words, you need to be blaming your ISP, not D-Link. The manual for your router clearly indicates updating the firmware is a manual process. The manual also clearly shows how you can manually select your own DNS service provider, go with your ISP's, or even use D-Links.
So again, if you cannot manually make these changes, it is because that router is defective, or more likely, has been modified and provided by your ISP. So again, don't blame D-Link.
Also, you say it was 2 years ago. I note D-Link India has released two firmware updates since then, one in Jan 2017 and another as recently as October 2017, as seen here.