So, if you want to run your old version, run your old version. No one is forcing you to change. You have the choice. However, like all choices, they come with consequences... in this case, running an old version means you get an "annoying" (but harmless) warning message show up. It doesn't affect the usability or functionality of your client in anyway... or your ability to "help" with maintaining the decentralisation of the network.
There are plenty of alternatives to simply upgrading to the lastest version of the software you're already running. You could even choose, as ETFbitcoin suggested, to run a completely different implementation... or you could even modify your current one to your liking by altering the code to remove the message and recompiling.