Instead ask why they feel it is average, that is a much healthier discussion and the whole point of a forum.
Guess ill start so we can hopefully move on from the "why dont you like this?!" nonsense.
I agree with a couple of your critisms, the whole hacking mini game, even though its amusing enough wont stay that way throughout the game and it really does take you out of the atmosphere its building during the levels.
It could be a welcome refreshment period for people that dont like the "on-the-edge-of-your-seat" atmosphere. And atleast they added a buyout feature to speed it up / by-pass it. I actually found the "on-edge" to be fairly nicely balanced, you have a few moments where you see/hear a shadow/sound and get an anxious tingle running down your spine, but most of the time i was searching around empty rooms looking for epo/bullets/cash/etc. Although i get where you are coming from as i couldnt even finish the first level of doom3, partly due to dying, but mostly due to walking around in the dark and then a big ugly, bloody beast leaping out at you (from a space that was emtpy a second earlier). I didnt enjoy that, and i also had that feeling years ago with resident evil on the ps1. It/I was just too "on edge" during those games. This one however strikes a nice balance, for me atleast.
As for the story, well i dont really know whats going to happen. Dttn know if you have, or what you know from the demo. I actually like the whole underwatercity experiment gone wrong and you end up in it. I am hoping during the game that you can find some "friends" as im sure being down there on your own for the whole game could just be a bit too much. Atleast the radio is helping to combat that.
And i really like the setting aswell, the whole art deco architecture and interiors really adds to the whole story/period for me. I also recognise a lot of it from study (statues, building facades, posters, etc) which brings everthing together to make a really believeble "world". Its probably one of the richest settings to have, contemporary settings dont really do much for me, and far future settings dont do anything for me. And neither does the whole medievil/oblivion setting so im pretty much left with 20th century and late 21st century. HL2 falls into this catagory for me, i cant remember what year it is in the game, but other then the alien/planets stuff its not too far in the future with the architecture, buggy/boat, etc.
For me it ticks all the right boxes, but there are a few elements in there that if you just dont like it; (like I dont with oblivion, even though its a great game) the setting, atmosphere, story, then the game just wont be for you as they are very dominant and important elements in the game. I'm really looking forward to fallout3, but the whole combat system of placing your attacks in a row and then watch the fight happen could be a game breaker for me.