Ran into this spot playing 25NL 6max on BCP. Villain was fairly new at the table so not a lot of reads.

UTG [Villain]: $29.57
BB [Hero]: $61.30

Preflop: Hero dealt Ac6c

UTG raises to $0.75, 4 folds, Hero calls...

Flop ($1.60): 2hAd5c

Hero checks, Villain bets $.75, Hero calls...

Turn ($3.10): 6d

Hero checks, Villain bets $1.75, Hero calls...

River ($6.60): 7d

Hero checks, Villain bets $3.25, Hero calls...

Villain shows 5d5s
Hero mucks

At first glance calling down 3 streets seemed pretty standard to me, figure he has A10+ a vast majority of the time and AA only very very rarely but probably doesn't take this line. I didn't put him on 55/22 since he opened UTG but I guess at these stakes a lot of people still do, and definitely wasn't worried about straight/flush. Can we fold this river/raise the turn? or is X/C, X/C, X/C the best play?