If you have a good post quality and descent rank then multiple campaigns will welcome you but there are many campaigns that allows jr member rank to join them so its a blessing for new comers who wants to start earning bitcoins and as they upgrade their ranks they can expect higher income in bitcoins.
Earning from campaigns is not at all a decent package and it is just an additional boost in your savings and nothing else.To say the least there are not much campaign that accepts people now a days and most of the campaign are here for a few weeks and some are really low paying ones and yes the payment are better than using faucet but it is not worth it at the moment.
Yes, I agree, signature campaigns are not a great source of bitcoin, especially when someone is really interested in getting rich in worth of bitcoin. And OP is also right, if someone is really interested in getting huge amounts of coins he should seriously think in purchasing them with fiat money, but unfortunately most newcomers seem to be only interested in free coins.