TINZ: My entire party was killed in the early game crypt, but I can't find a way to revive them as they are fallen within a necrotic fluid pool. I have waited, rested, even gone to camp but the fluid never goes, so I can't revive them. I must be doing something wrong. I also found this first crypt fight very hard. Although they were the same level as me, I was outnumbered 2 to 1 and some of them could do a ranged attack and also a melee attack. I was slaughtered many times. I am using balanced difficulty.
Are you trying to revivify your characters in the exact same position they fell? When you use the revivify scroll, you can place them on a nearby, non-hazardous location.
If it's the crypt I think, I had a different experience for a couple of reasons: by the time I tackled it, I was 1 or 2 levels above the enemies and I managed to use the Intimidate skill to get rid of a bunch of them from the start. So tip 1, don't be afraid to leave and come back later. You might find other enemies easier, if only because you have a particular party composition. Tip 2, if you have a party character with Charisma based skills like Deception, Intimidation, Persuasion, you can sometimes talk yourself out of fights. In my case, that's my PC.
In general, Larian games are a bit unusual vs other RPGs. Their encounters can be more like puzzles, trying to figure out how to combine all the tools you have available and there are a
lot of tools in BG3 to get to grips with, such as the various ways spells, items and class features can be used advantageously. Also in BG3, you have the ability to stealth ambush the enemy, which wasn't an option in DOS1 and 2. If you do this, you can sometimes get a free round as the enemy are Surprised and cannot take actions.
Another thing Larian likes is environment effects. With this crypt, there's a couple of ways of entering. One way allows for a situation of using the environment to easily kill a bunch of the enemy. Actually I'm not sure if you mean the ruins in general or the crypt within it. I've been talking more about the ruins in general.
If you're new to DnD and/or Larian style games, you might also consider the Explorer difficulty setting until you're more familiar with the game and rules. With such a huge game, you'll still have plenty of game left to play at the Balanced setting.