I’ve got a 13yr old daughter and a 15yr old son, they are both like your son to an extent, YouTube, Roblox, online gaming, any suggestions to go out are typically met with a “meh”. How was school? “Meh”. Why not ask him what he would like to do, is there somewhere he would like to go or do with say a friend tagging along? My kids love a day on the beach and they especially like taking a friend along. Sometimes it’s best not to tell them or ask them what they want to do, just say we’re going out for the day, mine normally have fun once they are there, be that a trip to the zoo, find a local stream, let them be kids etc. Hope this helps!