We are not using anything that is overidden by the new version, and yes the things that were rewritten are not necessarily compatible (and WOTC said this). This includes the old Human Race.
We are still using old feats that lack the +1 boost and they still work as good as they ever did.
However that leaves a ton of old stuff that is compatible, including the vast majority of FTOD.
Can you cite specific feats that were not overwritten and do not work now?
I will readily admit feats that were overwritten are not compatible, but the vast majority of others are.
The things that were weak prevoously are still weak, but every bit as compatible as they were before. Races like Half-Elf and Half-Orc and Goblin are still perfectly doable.
Feats like Eldritch Adept, Martial Adept and Mobile that were not reprinted are still about as effective as they were before (i.e. ok but not great), others like Elven Accuracy and the giant feats are still top tier. Feats that were weak in 5E are still there and are still weak, but they work.
One of the weak feats from old 5E is flames of Phelthegos and it is working pretty awesome on my Eldritch Knight/Warlock. Better than it ever did in old 5E (because of synergy with Agonizing Green Flame Blade).
That was XGE I believe, so 2017, not really "late".