Like many have said, it depends on what you're aiming for. You certainly can squeeze more than 2 cents out of 1 UR. I've redeemed 75,000 Avios (1:1 UR redemption) in the past 4 months (and never flying on BA metal) and gotten somewhere in the range of 4 - 10 cents out of 1 UR. It can be done but will require the time to put into finding how you can maximize it (I consider that part of what's fun about doing this).

It also is heavily dependent on what programs get devalued and if you can make a booking before that happens.

So the easiest path is definitely the 2% cash back card. But as in real life, the more you put into it, the more you get back out.