Depends primarily on prior agreement.

If before being drunk both parties stated something along the lines of "let's get drunk and have sex" and both agreed then it is obviously consensual. Grabted consent can be removed at any point but if neither party states/shows intention to back out it is safe to assume that there was consent during the act even if both parties were drunk because they'd agreed to it beforehand.

An important distinction to make is between the prior scenario in which both people agree with each other and one where I (hypothetical I) go to an event where it is explicitly stated that there will be a lot of alcohol and sex, I know of this fact and I agree that I want to have sex whike drunk. This is because while the assumption of consent still holds true it is an assumption as I need to know beforehand what I'm getting into and it's not exactly a given that I would consent to having it with anyone at that party over specific people. This obviously complicates things. Essentially everyone involved would need to be on the same page as tonwhat they're getting into and agree beforehand that they want to have sex whike drunk and with whom.

If there's no prior agreement the safest bet is don't have sex with drunk people. Naturally if both are at an equal level of drunkenness (≠ equal amount of drinks) it is difficult to assign blame but that doesn't mean both consented. It also depends on the level of drunkenness: two buzzed people who are still capable of understanding what is going on, can still communicate and are just less inhibited can probably still consent, two passed out drunk people cannot consent.