Just keep doing them. You will slowly accumulate enough dungeon knowledge until you feel confident at every pull of the dungeon. Just make sure you always know why your group failed. It’s best to record your gameplay, but if that’s not an option then just take the time after a failure to make sure you know why. Look at death details and see what people are dying to. If you aren’t sure go join some class discords and ask around. I still do this despite having done each dungeon countless times.
Unless you do a lot of “homework” (which sucks), the way you are going to learn is through repeated wipes and learning what went wrong so that next time you can try and make sure it doesn’t happen again. Unfortunately, low keys don’t do a great job at getting you ready for higher keys because many things that can be ignored in low keys suddenly start killing you in mid level and high keys.
The biggest cause of wipes is going to be dangerous casts that go off or a cast overlapping with unavoidable damage. It just takes time to learn what is important to kick. I highly recommending downloading something like plater and using a good plater profile (Quazzi has a great one that many people use). His profile color codes every mob so that every caster’s name plate is pink and every mob that does a frontal is teal. Anything that looks like a heal, like it has the word “heal” or “rejuvenating” in its cast is a must kick. Anything with the word “volley” is a must kick. Usually “bolts” aren’t too dangerous as they are single target low/mid damage spells…with the exception of the rookery lightning bolts…those truck and are also must kicks, but again you will learn all these over time…and also, most of these don’t even truly 1 shot until like 14s or higher…but they can bring your HP low and cause deaths with overlaps…or if you get unlucky and get double/triple targeted.