"I'm looking for the MAN in the MIRROR..." Michael Jackson
That's your answer...
It seems like a riddle, but it's very plain. You answered your question in your question! You are [aside from your age and orientation] a masculine and muscular guy looking for others with the same qualities, to connect with. Start there! You can introduce yourself to other masculine muscular men where I'm sure a lot of them spend time: THE GYM! Similarly, I'm sure the other masculine muscular guys have masculine muscular friends. Somewhere in there you can probably find some who happen to be in your age group and of the same sexual orientation!
I couldn't leave you without touching something else you wrote. You made the assumption that younger men aren't sincere. Be careful not to generalize "most" by the experiences you've had with "some!" I'm sure you don't want to be generalized by the mistakes of your peers. One day a young masculine muscular sincere man MAY come along and change your whole world! I promise not to say, "I told you so!" Keep your eyes, ears and your mind OPEN!
From my lips to your soul...
Redd