I've been a regular Strava user since about 2012 and it's been my sole log since maybe 2014. When I started using it you had just the locally competitive folks on there, but not the elites. In my area (fairly big running culture, San Luis Obispo CA, home of running warehouse), in that time I'd basically get every KOM if I ran any faster than easy pace, other than on tracks.
In around 2013/2014 I started getting too into the monthly distance challenges and was running extra miles just to stay in the top 50 for that month (top 50 is the first page). People say that strava makes people overtrain to show off, and that was my single experience with that type of thing. A couple years down the line, the mileage I was doing (maybe 75 mpw) didn't even get me in the top 200 on those month challenges, so I stopped caring about that anyway.
Segments were't competitive until about that time as well (2014ish, in California). Once they got competitive, you had some people stop caring about them because they couldn't compete, but you also had people creating new segments in their neighborhoods.
My thoughts on the changes...I could just say that I only care about the segments I'm top ten on anyway so this doesn't impact me much, but that's not true as I'm also somewhat of a cyclist and I can't even get top 100 in those popular segments. The feature I like the most is the heat maps which you can find using the route creator/building tool, which is now for paying users only. That alone is worth the monthly fee, for me definitely but also for anybody who travels much or enjoys finding new places to run.
comparing segment performances was also neat if you were close to getting a KOM and needed some extra strategy for pacing. It's also great for analysis of races because you can create a segment for the race course and see how you did compared to others from past years (whereas you could always use fly-bys to see how you compared to other races on that day)
The changes are rolling out over the next two days so you might not see anything yet.