What you experience is pretty much normal for any level of key when pugging them.
I’ve been in keys in the past where one death from the first pull causes people to leave (mainly the tank or healer first). It’s rare to see a dps leave first unless there are a type of player who thinks one death is the end of the key and can’t be timed. (or in a case I once had a dps being called out by the healer who died on the simple mechanics they had complete control over when I puged tanked)
Don’t ever let your first key experience discourage you ever. It might inflate you a bit, cause you to question yourself or the system but never let it defeat you.