To be honest I was reasonably late to Strava, only really joining it in 2013 since I always found MapMyRide more than met my needs- I wasn't overly concerned with my performance and just wanted to record my routes. However since so many people I knew were on it, it was inevitable I would drift towards checking out how quickly I covered certain segments rather than my average for each mile.
I still upload to both platforms since the data in each is useful for different things, but the one change I have really noticed as more and more people sign up is in regards "kudos". When I first started "kudos" were given by fellow cyclists when you had done something decent on a ride- a new PR, an impressive elevation total, a century or above- you had to earn them. Now however they seem to have developed into a Facebook style "like"- more or less some of your acquaintances simply signifying that they have seen you were out on your bike. This then leads to a cycle of simply giving them kudos, again for often ordinary runs, out of politeness and the whole thing loses any value it has to start with. It has been really noticable on my own feed recently- my form on the bike has been shockingly bad compared to earlier in the year- I have even titled rides "Pathetic" but still get kudos I haven't earned! Maybe I am taking things too seriously but I only want those thumbs up when my average goes back up (or at least when I come up with a humourous or inventive name for a ride!) as opposed to tunring into Facebook where my mum will "Like" anything I put up!