That is a MAX% run which is probably long as if not longer than running GTA 5 or San Andreas in one go. A better category would be a RANK1% category which has you do:

All GP (estimate 1hr: 45mins casually)

All Rival Time trial (Estimate 20 minutes, 4 time attacks)

All Duels (estimate 20 minutes, 4 races )

Battle Royal (1 Duel class machine Race, estimate 5 minutes , outer pass)

99 trial (1hr:45m hours casual)

Total :4 hours 20 minutes estimate.

These things will get you to Rank 1 which is True completion in this game and the actual career mode goal. This is achievable on any difficulty so the category can be split between each difficulty and console and emulator.

These estimates are for normal difficulty and factor in loading and normal playthrough menuing (so no optimal cutscnee skipping and navigation) between each step but I play on Emulator so I have no idea how long/ bad loading is on console (the game is on a CD iirc so I can only imagine its very slow) .

i am also estimating things as if playing casually/ at average pace VS going off speedrun pace so the category should actually be waay faster than the estimate.