You've been unlucky then. First video I saw on youtube this morning was someone squealing that Amazon had locked his
firestick due to his kodi activity :) Moaning that he had to make a fake Yahoo account just to sign in, he has a fair point, but that's what you get when you buy from the big boys. In the pocket of the government yet they won't pay their taxes!!
My £40 cheapo Qbox has had 15, 16 & now runs 17.1 like a dream.
It is also possible to now update 4.4 to 5.1 which lets you put kodi 17 on your old box and really just try to buy a rooted box or get it rooted.
Even if all that fails and it goes out of date, when all's said and done you're talking about a £30 - £40 object that's saved you a fortune in the 2 - 3 years you've used it. If mine blows up tonight I've saved £1928 - good scrap eh?