Budget and time spent does not always dictate quality. There are ways to make a better AAA than Red Dead without spending nearly as much time on the game.
True, but alot of things that make RDR2 better than AC Odyssey are things that are directly a result of the higher budget and higher man-hours. For instance the horse riding, the level of realism that went into the horses in RDR2 in terms of level of detail and animation quality are directly a result of RDR2 being a AAAA/AAA+ rather than a AAA, they probably had a whole team dedicated to the horses that worked on nothing but the horses for at least a year, AC Odyssey just couldn't compete against RDR2 in terms of horses due to the fact that Rockstar had the budget to throw alot more man-hours into the development of the horses than Ubisoft had. Another for instance would be the much greater variety of flavor dialogue, that comes down to Rockstar spending the money to hire a voice cast of over 1000 actors to provide tons of flavor dialogue for the many NPC's you encounter while exploring the open world. In the end, RDR2 having better graphics than AC Odyssey largely comes down to Rockstar throwing more man-hours behind the development of the latest iteration of the Rage engine than Ubisoft was willing to throw into the development of the latest iteration of their Anvil Next engine, it's rumored that the whole first year of development was spent upgrading the RAGE engine for current gen consoles with ongoing improvements throughout the rest of the development.
Now of course there are things like writing that are better in RDR2 which don't really have anything to do with the increased budget and man-hours, Rockstar just picked a better lead writer for RDR2 than Ubisoft picked for AC Odyssey.