My stock answer is: "Thanks guy, but I'm afraid we are not a match... I like to let guys know, so you do not waste your grueling (insert app name here) time on me when it can be utilized with someone else more suited for your needs.... Good luck..."
I actually had a variation of this phrase sent to me when I started chatting with someone online a few years ago... It made sense to me, so I added it to my saved phrases and have used it on other apps... Last time I used it was 2 days ago, a 19 yr old messaged me with just the unlocking of his photos, no greeting, etc... I wasn't interested, so I sent my response... He replied with "Thanks, Man" and then "Much Appreciated"... I said "You're welcome... I understand exactly what it's like, so why be a dick about it..." He said: "I wish there were more like you"... We then chatted for another 20 min before I needed to leave for the gym... Turns out, there could be some interest on my part after all... Now, had it gone a different way, I would have just blocked him...