We have some very good friends who are enthusiastic game organisers. They know we’re not keen. When invited to their home along with family, who expect and appear to enjoy the games, it’s understood we might join in with one at the most. Otherwise we top up drinks, disappear into the kitchen and tidy, bring out some food or simply sit and be an audience/keep score. No one minds. They probably do think we’re odd but it doesn’t stop the invites coming.
Can you not have a quiet word madwoman and say much as you enjoy their company the attraction of games has worn off. Make light of it, don’t sound as if you’re complaining, be regretful while not overly apologetic. It it’s the truth you could add something about physical health - an increase in pain the next day, headaches if you need to look closely at anything, exhaustion from the movement. Only if it is truth though, best not to fabricate illness.
If speaking to them seems impossible. maw’s strategy of the date not working (without explanation) followed by an invitation to your home in the near future surely can’t cause offence.
Be brave, if your friendship is sound it will survive.