This is just about the worst criticism of a story anyone can make. High school lit class nonsense. If you have to like a character to care about a story you've jettisoned a tremendous number of excellent stories for a completely arbitrary reason.
And that's leaving aside the absurd notion that RDR has no likable characters. If you were just talking about the overlong middle act of the game, I'd kind of be on board but sorry dude, you're off in Crazytown, Population: 1 on this one.
If a game expects you to care about your family enough to reunite with/save them (the entire point of the story), yea they should be likable, which they weren't, and neither was Marston.
Likability matters a lot in certain contexts. It's one of the reason's God of War 3's ending makes zero sense given how shitty his character is throughout the entire game.
It's pretty rare for people to care about a story when all of the characters are either really bad people morally, or really uninteresting ones. House of Cards is the only example I can think of right now where people find enjoyment in the widespread pessimism/hopelessness rather than the optimism.
You're right though forcing me to do like 4 hours of rounding sheep so that I "form a bond" with my dumb annoying son and pressing x for 15min to travel to empty X town in order to shoot no-name Y guys is awesome. The sappy ending does nothing to retroactively fix all of the weak shit that came before it.
Like I said, all of the stuff people supposedly hate GTA4 for, they completely ignore or tolerate in RDR for reasons I don't understand. (I didn't dislike GTA4 either btw, but in RDR those problems shine like the sun).