Ok. I'll bite. For example?
BG1 is more coherent and interconnected in terms of locations,
You mean random pointless wilderness maps, like Pillars of Eternity?
it has more variety in its wilderness areas,
No idea what this refers to. "Variety" is one of the last adjectives I'd use to describe BG1's wilderness areas.
you aren't assaulted every 10 seconds by NPCs with random quests or banter,
If you do not want banter, EE let's you generate all 6 party members. Pretty sure there are mods that do this as well.
low level D&D is widely considered to be better than the higher level one,
So if you buy this argument, every low level DnD scenario is superior to BG2? Shadow Sorcerer? NWN?
the mage duels which people like so much make an appearance in BG1 too,
Part of what makes BG2 awesome is the high level spells that your characters and enemies can cast.
BG1 feels more like an adventure than a scripted corridor,
Not sure how BG2 feels scripted or does not feel like an adventure when its remembered for enormous side quests including the Shadow and Red Dragons.
the SoA story is irrelevant to the actual narrative of the Bhaalspawn,
... this is a weird criticism of the SoA plot, but I get your point. Still I would counter argue that even if you do see all of SoA as a random adventure that doesn't advance the Bhaalspawn saga much, it is fully in the flavor of FR literature like Drizzt (Icewindale Saga) or Avatar trilogy, or even older pulp fantasy like Elric or Conan, which BG2 is trying to capture.
even SoA's prologue is worse than Candlekeep,
This is just blasphemy. Chateau Irenicus is one of the best examples of a starting area that teaches you how to play the game, but isn't forced or too popamole. You get right into the action.
BG1 has one of the best dungeons ever made - Durlag's Tower, Watcher's Keep can't hold a candle to it,
Super subjective. And you want to compare dungeons, Spellhold is a great dungeon. But the real point is BG2 maps feel like real places, not forced dungeons like Durlag's Tower.
BG2 adds a lot of unnecessary and overpowered kits, writing took a huge nosedive because they wanted to be epic and "complex", etc. etc. I can go on forever.
Only agents of decline prefer BG2 over 1. BG2 is not a bad game, but it's inferior to its predecessor in almost every possible way.
Kits add to replayability, and some kits are very distinctive, for example Valygar's Stalker kit or Yoshimo's Trapper kit. But complaining about kits is tedious nitpicking.