As for fanaticism I'd say that neither All4BigGuns opinion that good non combat RPGs are impossible, nor Katrex's opinion that mechanics distract from story are examples of it. I'd just say that its two players with different styles expressing their preference. The fact that Guns got a reasoned response and Katrex got called a fanatic is an example of the behavior I've been objecting to here.
Really? Because the way I read it, Katrex just outright dismissed any possibility that a background, no matter how detailed or well-characterized,
after you start on your sheet might create a "genuine" character, and declared that the One True Way to build a character is to write your background
then, and only then, once the background is set in stone, fill in your sheet.
Probably just an unintended implication of the word-choice, but it's the same style of dismissal I hear from certain religious types when they foo-foo scientific knowledge that contradicts their religious dogma.
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Now, as for Katrex's own commentary...
There will be people forced in to the shadows who at the start DONT have their core competancies,
Problem is, 400 BP characters aren't "noobs". They're right at the start of their career, sure, but they're supposed to be developed enough to actually get booked for "real" work by a Fixer. These people aren't charities and, as said before, your teammates aren't there to baby-sit you. If you can't do your job, why are you being hired instead of one of the guys who can?
And don't get me wrong, there's a world of difference between "the best of the best" and "good enough." I think that message may get a little lost in the shuffle, some times.
You've got to start somewhere, and people aren't going to be paying the money the Big Dogs demand to do jobs like a simple grab'n'go theft or low-security extraction, but there's a point where you have to ask yourself why they're bothering with you when the out-of-the-book Gangers are just as good, and will probably work for cheaper.
Let's take a corp wageslave that finds out too much and has to go on the run. Saying "oh hes not good enough mechanicly" so he then becomes a gun fanatic who went to the pistol range every other day to get a 6 in pistols
That's viable, and im not saying its wrong. It's created a character with a back story. But it does detract from the fact that at first your idea was this is an ordinary guy who gets mixed up in the wrong business.
If he's a trigger-man, then he dang well
better have some shooting skills at the start. Otherwise, again, why did he get hired as a trigger-man?
If he's
not a trigger-man, shooting isn't one of his "core competencies" anyway, so it doesn't matter if he can't shoot. Sure, it's a
good idea to be able to handle a gun, given the line of work, but it's not the Face/Hacker/Whatever's job to sling lead, so it's not a huge deal if they can barely hit the broad side of a barn.
I would, Give him in debt and with a basic skillwire, have him perhaps get addicted to combat drugs in play, max his edge even if it isn't optimal, because he is damn lucky hes somehow survived this far, high mental stats even if he isn't a mage or technomancer.
He wont be as optimised but for me anyway trying to roleplay how he would deal with the horrors of the shadoworld, is much more interesting than, the guy in the same situation who was a corporate experiment whos auged up to the teeth and spent his childhood hunting animals and is therfore no stranger to death.
That's a bit of a straw man, there, Katrex. You don't need to be some freakish, SURGEd vat-job to be "competent." Just take all the common and customary steps that anyone would reasonably take to be good at their high-risk-high-reward profession. Stuff like a trigger-man having Muscle Toner 2, an Agility of at least 4(6), and a Shooting Skill of at least 4.
10 dice before modifiers isn't too high a bar, is it?
As for roleplaying horrors... how about a kid that grew up half-starved in the Barrens and learned how to fight because it was that or keep getting the shit kicked out of him by bigger kids who wanted what little he had and, eventually, got noticed by one of the bigger gangs and got some more skills and access to some 'ware (probably Second-Hand, of course), and is finally "graduating" to being a Shadowrunner?
The very fact that the kid sees those horrors as "the way things are" has its own potential for gritty, GrimDark nastiness if you play up the "hardened" attitude, rather than simply dismissing it...
especially if there's a sheltered Wageslave type in the party as well to get freaked out over it.

I hope you understand the distinction Im making. And im not always doing it, i also often do it yourway. But i think this way does create more interesting characters to roleplay, Although granted it can be as if you're playing on hard mode.
I wouldn't call them "more interesting" as much as simply "less professional."
That's not a bad thing, mind you, but it's not everyone's cup of tea. It really depends on what you want from the game, and how you, as a player, are going to interact with your character on a meta level.
For example, I enjoy social RP, especially if it's random stuff happening during "slow points" in a job when we have to wait for something, but I don't want to spend 3 sessions on down-time chit-chatting with family and friends. I get enough "just folks" RP on the MUSHs I play on.
I also take pleasure in designing, planning, constructing, and generally "scheming" type activities. That means that 1) optimizing a character while preserving their uniqueness as an individual entity is an enjoyable challenge in its own right, and 2) I need to play a character that can reasonably do the same things... because, otherwise, it's just no fun for me. I hate not being able to actually act on the tactical insights I might have because it's not the "in character" thing to do.