The Siri Watch face has been an unexpected gem for me - it is limited but still very useful. One thing many people miss is that you can customise the data sources for the watch face - so if you don’t want to see reminders to breathe, or the stocks then you don’t need to.

The Siri watch face only allows you to have one complication, which complicates matters somewhat (pun intended!). I have chosen Carrot weather, because the weather in Vienna tends to stay somewhat stable throughout the day, this means I can turn off the Weather source in the watch face.
What is limiting is that 3rd party app developers can’t integrate into the Siri face - at least not directly. I have managed to get my OmniFocus data into it though - by subscribing to my OmniFocus calendar on my iPhone. This calendar is hidden, and does have the unfortunate side effect of giving me an extra notification when each task is due if I let it get that far - but for me the trade off is well worth it. You can manage the calendars shown on your Apple Watch in the Watch app, under Calendars. I don’t have this mirror my iPhone as I am subscribed to many calendars and toggle those on and off as needed - but I still don’t want birthdays showing up on my watch face as that’s a bit late reminder wise!
Throughout the last year the Siri face has been very successful in providing me the data I want when I want it - possibly because I don’t have many data sources enabled. If you tried it before and gave up on it then I would recommend giving it another shot - perhaps with less data this time.