"Wall Street" as popularly imagined - the world of big banks like JPMorgan, Goldman Sachs etc. don't invest in anything. Wall Street's role is threefold:
- Providing access to capital and dealmaking facilities for companies looking to grow or change ownership. That's IPOs, debt issues, mergers & acquisitions, spinoffs, corporate restructuring. Banks organize those deals and shop them around, acting as advisers.
- Facilitating trading of securitized instruments (public stocks, bonds, derivatives) by making markets or otherwise connecting buyers and sellers to exchanges or other counterparties. These buyers and sellers are the funds actually investing in individual companies and retail brokers servicing individual investors. The bank is neutral in its view of the issuers of the securities being traded, it just wants to see trading happen. (Sometimes this involves creating a specific instrument for one client and selling offsetting instruments to others, but again the intent is that the bank is not taking a position in that client.)
- Providing banking services to corporate clients. Loaning them money, helping them manage exposure to foreign currencies, and so on. The kind of stuff any retail bank does for its individual clients, but scaled up.
> Idealist me thinks that Wall Street should invest in those companies they believe in and wish to assist in achieving their business goals.
Your idealist premise is also a bit frightening if you think about it further: you're suggesting that an industry with a purely facilitatory role - i.e. offering access to public markets - should use some sort of qualitative moral judgement on who it should provide services to. That's a dark path.
Fortunately your industry does exist: it's called the buy side, and there are fund managers out there who will happily take your money, pool it with others, and invest according to a thesis they are legally obliged to share with you and stick to.