Nadav and Avihu's punishment seems harsh, especially if their sin was drinking a little wine. An analysis of the philosophy behind the prohibition of DUI reveals why their penalty was so severe.
From the passuk it seems like the sin was "lo tosif". I think that it wasn't that being drunk was a itsself a sin but that because they were drunk they changed the avodah, and that was a sin.
We see from Adam Harishon that lo tosif can carry a chiuv of misah. Because Adam/Chava added "don't touch the tree" they provided the snake an angle of attack. And the result is that they (and everybody since) became mortal.
Would point out that we find a difference between Avodas hamikdash and Avodas halev. The former is invalidated even after one has imbibed a reviis of wine but isn't yet drunk while the latter is only invalidated when one is halachically defined as drunk (אינו יכול לדבר לפני המלך). Compare https://rambam.alhatorah.org/Full/Biat_HaMikdash/1.1#e0n6 to the one you cited.
From the passuk it seems like the sin was "lo tosif". I think that it wasn't that being drunk was a itsself a sin but that because they were drunk they changed the avodah, and that was a sin.
We see from Adam Harishon that lo tosif can carry a chiuv of misah. Because Adam/Chava added "don't touch the tree" they provided the snake an angle of attack. And the result is that they (and everybody since) became mortal.
That's been my reading as well. And yeah, that Adam ha'Rishon example is a powerful one!
Second to last paragraph, second sentence, you missed a word.
"they <run> the risk"
Thank you!
Would point out that we find a difference between Avodas hamikdash and Avodas halev. The former is invalidated even after one has imbibed a reviis of wine but isn't yet drunk while the latter is only invalidated when one is halachically defined as drunk (אינו יכול לדבר לפני המלך). Compare https://rambam.alhatorah.org/Full/Biat_HaMikdash/1.1#e0n6 to the one you cited.