The bulk of investment bankers are not picking stocks for funds. In the field of fund management, there are some people doing this, and it is a very common trend that passive indexes do better than the active funds - it is true.

In the field of investment banking trading (which is mostly market making) the amount of automation varies by asset class: very automated for some asset classes like fx, equities, much less for more illiquid asset classes like credit, commodities, bespoke products.

As well, senior traders operate as the 'business' making more decisions than pricing of products. They make the business decisions often judging legal, compliance, accounting risks. (and not always correctly.).

e.g. do you accept to trade with a Dutch counterparty who wants to trade against your German legal entity knowing that you can only hedge the position in London? What is the risk between the two legal setups? What premium should you charge for those risks?

Do you trade the very large size that the counterparty wants, knowing it takes you over your balance sheet position limit - can you get approval for this from your senior management? Can you offset the position in the market without it moving against you? What premium do you charge for this?