Sorry for my ignorance, as it's not something that I've really looked into. I'd love someone to give me a little heads up, the reason why it's a big deal?
An important point about updates that's been made a few times over the years: Samsung isn't selling you the Galaxy S7 with a grand vision of how awesome it's going to be when it gets updated to Oreo two years later. They're selling it to you in the hopes that you love what they did with the software as it was when you opened the box.
Well there are three kinds of updates: 1) Major OS updates, like going from Nougat to Oreo 2) Incremental OS updates like going from 7.0 to 7.1 and 3) Security updates. Samsung does 1 and 3, just slowly though on 3 they are still better than most OEM's out there. On type 2 they typically ignore those entirely. 1 and 3 are definitely the most important, with I think most of us in the forums leaning towards 3 as more important than 1.
Type 1 updates are generally bringing new features - however, with Samsung, these can sometimes be features they already had, just with a different implementation that serves only Samsung devices, while the new updates typically does it in a way to get it to all kinds of devices. An example is mutli-window. With the Samsung version, it was kinda jenky and only worked on certain apps, but they had it two years before the rest of Android got it - but now that Android has it, it actually works better and for more apps. As an example of this, Oreo was released last summer and many 2017 Samsung phones still do not have it.
Type 2 updates are generally bringing polish to the major update and lately, for the last couple of years, there has only been one of these updates and it usually follows the Type 1 by only a few months. Call it a finishing update. 8.1 was released 3 months ago and so far Samsung has put it on zero devices, including the S9.
Type 3 updates are monthly security updates, which Google provides the code to the OEM for about a month prior to their release schedule, and then the OEM pushes the update out. That's the one that people tend to get grumpy about. As an example of the issue here, some Samsung devices are on the February update right now, some are on December. March was released yesterday and is already available to all Pixel devices (this year's and last) as well as the last generation of Nexus devices from 2015. So best case scenario, right now, all Samsung phones are at least one month behind.
The bigger question is... should any of this matter at all, if users don't care? Most users don't - if they did, Samsung would change their priorities. But updates are not selling phones in any sort of significant volume. For some users this is a dealbreaker, for others it's the last thing on their mind. Similar to how not having an SD card slot is a dealbreaker for some users, while others don't care in any way whatsoever. Just treat it like another feature IMO, it's either important to you or it isn't.