I think the genesis for "you can't teach an old dog new tricks" comes with an increasing mental weariness to unproductive tinkering that you tend to acquire as you age, making you more inclined to use "tried and true" methods.
A while back, I was going through learning Adobe After Effects for a project, but found myself frustrated that I was not picking up the interface after a few go-arounds. Everything seemed unintuitive and unexplained. Just as I was about to go back to Sony Vegas, it occurred to me that when I was a teenager, Sony Vegas and other tools were equally unintuitive and unexplained, but I just messed with them until I found a solution. So I waited until I had a vacation to pick to dedicate my time to messing around with After Effects with Google by my side, and now its slowly becoming second nature.
I also have this conflict with GIMP and Photoshop, in that I always use GIMP because I am familiar with its quirks, but its hardly ever failed me and it is more cross-platform than Photoshop, so I find sticking to it to be worth the time-sinks in various particularities of the software.
I feel this experience highlights the necessity of experimentation, which people often try to bypass with an increasingly dated knowledge of a skill. And the more you hold out, the rougher the paradigm shift will be when and if you finally try and challenge it.