A lot of the more complicated and obscure rules in AD&D ("helmet rule," weapon speed vs. casting time comparison that involves an absolute value calculation, the entire DMG unarmed combat system, etc.) are definitely more trouble than they're worth, but I really fell in love with the AD&D surprise rules when I discovered them c. 2002 (after close to 20 years of using B/X D&D rules like everyone else) and wouldn't want to do without them. They completely change the shape of combat in the game, making high Dex (and the elf and halfling racial and ranger class surprise bonus) much more important, and making the primary tactical consideration of the game how to both achieve surprise and avoid being surprised as often as possible. Ambushes become much more common, using scouts (especially a high-Dex elf, halfling, or ranger) becomes much more common. Many combats that begin with one side having surprise (especially 3 or 4 segments worth) will be over before the other side ever gets a chance to react!
So that particular bit, at least, I'd be very hesitant to drop because, at least IMO, it improves the game and makes things much more tactically interesting. But most of that other stuff (e.g. "Attacks directed at spell casters will come on that segment of the round shown on the opponent's or on their own side's initiative die, whichever is applicable" -- with absolutely no indication how you're supposed to decide which is applicable!) I agree -- Yuck!
(Oh, and FWIW add me to the group surprised by the surprise/revulsion at the "declare actions before rolling initiative" rule in AD&D -- I've always done this, even before I was playing (or rather attempting to play) "RAW" AD&D -- at the beginning of each round I go around the table asking each player quickly what they're going to do this round, then initiative is rolled (by group, not by individual), then all actions are resolved in order (as decided by me); in RAW AD&D a declaration phase is absolutely necessary because different initiative procedures apply to different actions -- if you're moving a different procedure applies than if you're fighting in melee than applies than if you're firing a missile than applies if you're casting a spell or using a device than applies if you're attempting to grapple or overbear, etc. so it's absolutely essential to know what everyone is intending to do before the initiative dice are rolled.)