If you're asking about customization, I definitely cater my device to my preferences and needs. Customization goes a very long way and is more than just about aesthetics. Customization means the phone tries its best to cater to me, the end user. With my iPhone, because it's limited in customization, I find I have to cater to it, and that doesn't always jive.
However, are you also asking about raw specs? That's how I read the thread title. In that regard, my answer is no. I definitely don't use my phone's specs to their full potential. The games I play are rather simple. I don't really record 4K. Etc.
If you're merely just asking about customization, here's the beauty: it's your choice. You customize as much as you want or as little. Even tweaking a few small things here and there to cater to your personal usage can make a difference, especially when you consider that smartphones are devices we use daily, multiple times a day.
And once you're satisfied, you don't have to tweak anymore. A lot of people who don't understand customization often say that they hate having to change things over and over again. Who says they have to? You customize as much as you want.