You have outlined my 3 biggest complaints with Strava. It is so comforting that I am not a "unique and demanding snowflake" for wondering why these features don't exist. Other people have the same problems with Strava as me!.
Strava's lack of multisport has been driving me insane for years. Getting 5 separate activities is stupid, and it seems like at the very least they could figure out how to handle transitions so they aren't their own activity. Surely that can't require a ton of development time. I always have to go through and delete my two transitions (I still have the data in Garmin Connect for training records). This is especially annoying when you consider that they have people (like I used to) who pay $60 per year for premium subscriptions. Meanwhile Garmin is offering it for free with Garmin Connect (after you buy a Garmin device).
Don't even get me started on Strava's lack of support for swimming. Even as a premium (now called "Summit") member, you get nearly no analytics from swimming. It basically shows up as an activity and that is where the functionality ends.
Finally segments are a complete joke. There are segments in my area that even Usain Bolt couldn't beat. There is a 0.8mile long category HC cycling climb by my house that has a "record" of 54 seconds. So I guess I am to believe that someone rode up a 8% grade hill at 60mph? That would be hard to do on a motorcycle, let alone a bicycle. Surely they could figure out how to filter those out.