Recent Hondas use a Garmin-based built-in Nav system, and free quarterly updates are available from Garmin for at least 5 years. The update process uses the Garmin Express software, just like Garmin stand-alone GPS devices. What happens after 5 years of ownership is unknown.
Garmin gets its road maps from HERE, the same provider as for Acura built-in systems. But the updates for most Acuras get pressed onto DVDs for sale and distribution, so they probably lag behind the latest releases.
Don't even get me started on what's going on with 2019 RDX; it's a mess. And apparently NSX uses the Garmin system.
Anyway, in general I agree with purchasing an update every few years, or not at all.
Some map updates do include updates to the navigation software, including for 2014 MDX. ( They are provided on a separate install disc bundled with the map update. ) But unfortunately, 2014 was orphaned because of a hardware change going forward. It can't run the same software as 2015, which got enhanced ( semi-functional ) voice recognition as an update to the originally installed software. And there have been further changes to both hardware and software after 2015.
If you're after the "latest" archaic software for a 2014 MDX, consider getting a map update that has gone on discount because a new one has been released. Discounted discs are usually $99 vs $149 for the latest release. But you might want to check the revision level of your current software. It's available in the "settings" menus.