Yes, athletics count as serious EC’s. Especially if kids play on multiple varsity teams.
As for MUN, robotics clubs, tutoring and service: There are levels within each of these. For example a golden gavel winner at MUN and related is the kid colleges want not just the kid who went one year: robots has varied types of teams and levels up to global winners (there are also underwater robotics teams and many other variations); Tutoring and service can be quite varied from limited all the way to doing amazing things.
The odd thing is, if you read some of the chance me threads, kids often exaggerate their importance or extend their actual participation levels. You can tell this if your kid is in that activity and you are familiar with the levels and then read about what another kid did. It reads like they did something amazing when in fact it is quite a common thing in that activity. College admins are also very likely to know which activities are commonly done and the levels within each activity. An Eagle Scout/or a Girl Scout Gold Award winner, for example is not the same as doing boy/girl scouts for a year once a week, for example. And colleges know this.
Same with sports, kids on Varsity teams might not plan to play in college but they might have lots of awards and achievements in that area. Many kids will be all-scholastic, or MVP, or be asked to join tournaments etc. Those things are all achievements and the pages can run on if the kid is a talented athlete. Some sports things will overlap and some will not. And some sports kids will have fundraisers for community service projects.
Some sports, like track, are easier than others, to pinpoint achievements. But kids will also get the bonus from teacher/guidance recommendations that they were able to do a sport and balance school.