If you understand what a word was intended to mean, you're using it gooderest enough.
If you are using it in a way that was established 40 years ago and has been used consistently since then, you're using it in the most important way - understandably.
As for the 'promise that 5E would be the end all of D&D': One D&D is an evolution to rough off the edges, but so far it seems like the least change between editions that we've ever seen, and you may, in fact, be able to take a 5E character and drop them directly into One D&D with only minimal changes - likely about the same as you'd experience playing with a new DM with different house rules.
But putting that aside, and assuming that once One D&D releases every cent we spent on 5E will no longer provide us any benefit...
I spent $500 on 5E hardcovers. I spent an additional $1000 on D&Dbeyond. Since July 2014 when the 5E materials officially started to release, I've spent another $1500 on miniatures and $2000 on terrain and accessories. That is $5000 cash flow (roughly) on this hobby over 8 and a third years.
During that time, I have played about 2500 hours of D&D at the table, and spent another 2500 hours enjoyably worldbuilding/preparing as a DM. Further, I've spent about 3000 hours on Reddit, Youtube, Enworld and other sites talking about this game I love (and a few hundred more shaking my head at some members of the community). 8000 hours of entertainment, $5000. Let's bump it up to $6000 for costs to deal with all that pesky electricitiy I used as well as for things like donations to sites I use. 1.33 hours of entertainment per dollar I spent. That is ridiculously cheap and I consider myself in the top 2% of spenders on this game (although there are people that spent well more than $25,000 since 5E released - but there are far, far, far, far more that spent much less than I did).
I think I have received my money's worth.
And to be honest - every cent I spent was unnecessary. I could have run 5E for free. They gave us enough essential material, and the rest of the 'near essentials' it is out there through borrowing books, internet, etc... Many of the players that I've had at my tables over this past year likely spent less than $200 total over that entire period. Their biggest expense was likely the electricity to play online or gas to reach my place in their car.