Are Parkruns not just 5ks? I've seen people say we need them in the US, but I never actually looked into them.
All are accurately measured 5Ks and are great idea! There are three Parkruns within a 15-20 minute drive of where I live.
Two are more like an easy high school XC course along nature trail loops; so maybe 20 seconds a mile slower than a road 5K. I would love to run one at a one of the faster courses like Bushy Park in the UK.
One of our local Parkruns has a pretty small turnout, but the other nearest to us has had an average of 80 -110 participants pretty much all Fall.
The are IMO excellent for a Saturday morning tempo run. Free timed events and all they ask is you volunteer (set up, record keeping, tear down etc.) once in a while.
To say they are "accurately measured" is a stretch. Very few have been accurately measured, most are just done with a wheel bought from the local DIY shop. I know Pegwell Bay parkrun is short by around 300m so if you want a 5k PB, put it on your list.
I agree with everything else you wrote. Parkruns are great events precisely because they can be as competitive as you want them to be. I also like the variation in the courses. My local parkrun is a hard XC type course but I can travel 30 minutes to a pancake flat tarmac course as well