Kojima brainwashing people into thinking he filled plotholes that were never there.
Venom doesn't make anything make more sense. Big Boss never died in MG1, he tells you himself at the end of the game, in MG2 he's a cyborg because of his injuries. MGSV retconned all this and now BB being a cyborg doesn't make sense.
MG1 is even more muddled up than ever before since we don't know if Venom and BB were working together, if Venom went rogue, if BB betrayed him, which BB was talking to Snake on the radio, etc etc.
Nothing changes from MG2 onwards, Venom is irrelevant after MG1.