I view RWGPS as part of the problem. They offer a variety of ways to format the downloaded file (good, I hear you cry) but for any user and device only one of these is likely to be optimal and some of the others could simply be broken. As noted upthread, it is too easy for RWGPS to generate more than 10,000 points and for the user's device to truncate that file in use - too easy for otherwise sensible people to trust in teh magic and set off into the wilds without checking first. The fault lies with RWGPS for providing potentially incompatible files, with the GPS manufacturer for not providing clear error messages when there is an import problem, with the user for succumbing to a temporary bout of simple-mindedness.
My experience is a bit dated (I still use an old eTrex Vista HCx; it works), but I wonder if there is a standard that would be ok with all devices?
As long as there are old devices like yours still out there in the wild, the 'lowest common denominator' file (including the 500 trackpoint limit) cannot change. AUK published advice about this in the last hardcopy Handbook (distributed January 2014) and that advice can still be found on Aukweb under 'Hints and Tips'.
https://www.aukweb.net/hints/gps/Of course things have moved on a lot since 2014 and even back then this advice raised hackles in some quarters. It could of course be updated but how? - the lowest common denominator hasn't changed. But 95% of riders now expect (expect, not need) far more than 500 points and increasingly there is an expectation of embedded turn instructions. Organisers not recognising this would be bound to get some flak.