Here is SB with 4h6h.

CO is a megadonk. UTG is okish, Button is a good tight player. Everyone else is your standard mediocer 4-8 player.

UTG, UTG+2, MP1, CO and Button all call, I complete, BB checks.

Flop: 4s 5d 6s.

Hero bets, BB folds, UTG calls, UTG+2 raises, MP1 3 bets, CO calls, Button caps, Hero folds.

Yeah, bleh, I'm ok with it.

If UTG calls the cap 1/3 times and everyone else always calls, you are getting like 9:1
And huge odds - RIO or otherwise

If 55 is out there, then 4's are no good.
If 66 is out, we are dead to running 4's, or splitting boards

Is this OESD and FD raising and betting/calling?

With no preflop action, the board easily hits all sorts of hands .. super strong and great draws.

Personally, I'd have to see the turn. If the board pairs, you should see some defining action, right?

Remeber: The odds are MUCH higher that there are Straights out, than Sets. And for made Straights, you would need much worse odds to fold here.
Other than being shown 66, I'm in