That doesn’t sound right. It doesn’t have to be completely flat for wheelchair accessibility. Ever seen a wheelchair ramp? What it needs for wheel chair accessibility is some flat places to putt from, and slopes and ramps instead of stairs. The course can be angled whatever way makes it the most challenging from there.
If it was the case that the golf course didn’t have any elevated areas because they were trying to be accessible, that’s their mistake. There are ways to make things accessible and still fun for everyone.
Would I have the right, however, to demand access to everywhere I feel like going?
Actually, yeah. We do have the right to demand that places are accessible. If something is open to the public, it’s supposed to be open for all of us. Implying we don’t have a right to be there just because you think making things accessible will make it a worse experience for everyone is incredibly ableist.