None of these features were required back then because the particular "problem" did not exist. Most of these implementations are just features/commodities we know from other modern games.
Also, your no-lead was addressed by KM back then when both of you were not born. If I remember correctly the basic concept was to increase the network update cycle (this game was being played at a time when logging into the Internet made a noise)
Besides, features we missed back then were
-AI syncing
-Animation syncing
-Improved lightmaps (lol @Sapien calculating lightmaps for 12 hours just to crash)
-Multiple grenades
(and these are just some from the top of my head)
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