Ok fair point. Though I'll say in my experience I don't see people being weird out by 33/40 or even 33/51 in most cases. It's almost always with someone in their early 20s and it comes off weird when you know that the brain isn't even finished developing until years later. I think once someone reaches around 25-30 then they are truly considered "adult" in a more broad social sense.
Common complaint from people is that we send "kids" to war, but obviously most don't. We just know that's it's fucked up to make young people 18- early 20s make life altering decisions.
The brain is constantly changing. You are constantly changing. People do judge and do it very vocally. I think some are projecting and some are jealous. I suspect they will end up on the wrong side of history.
Ones values and interests change as life changes around you. Rather than trying to squeeze into the mold of those in your age group I prefer to spend time and conversation with those that share my current values, interedts, desires.
When I look back, and when I talk to others I find that age gap relationships have been some of the best.