With "Project Treble" is supposed to improve the update problem in the Android world - unfortunately the full functionality is only available for devices that were shipped with Android 8.0 "Oreo".
Almost the impression arises that the manufacturers are trying to slow Treble down intentionally: even devices that will be introduced in 2018 (and thus after Android 8.1 is released) will be delivered with Android 7.x first - only to be promptly provided with an Android 8.x update.
Therewith, the buyers of these devices profit from the new Android version, but don't get the remaining advantages, specially faster updates to the following Android versions. Faster updates - especially for devices below the high-end models - would be a positive development for many customers. From a manufacturer's point of view, this doesn't seem to be quite as desirable: otherwise manufacturers like HMD Global would deliver their devices directly with "Oreo".
This only affects the manufacturer of Nokia smartphones: Motorola and Samsung have also not launched their models with the current Android version. Especially off the top models "Project Treble" help.
Although quick updates are promised, one is still dependent on the goodwill of the manufacturer. The only thing left for the customers is to avoid devices that are not delivered with the latest Android. In the course of the year 2018 the situation will hopefully improve and more and more devices will be released directly with Android 8.x.