If you feel that the balance in Overwatch just isn't there yet, worry not as the next patch will give you the ability to essentially balance the various games modes to your liking. And best of all, due to the upcoming Server Browser you'll also be able to easily find other people to play with... assuming your newly created mode is actually enjoyable to mess around in.
While the concept itself may be quite simple, there has been a surprising amount of thought put into this new system. So if you're wondering about all of the details, allow me to share with you the recent Developer Update video as Overwatch's Game Director Jeff Kaplan does a damn good job of explaining everything you need to know. Have a look:
I've briefly messed around with the Server Browser on the PTR, and while it is most certainly clunky I can see a ton of potential in it. Right now its mostly a portal to wacky balance changes and some truly ridiculous duels, but after a couple of major patches it could be the powerful enough to support a proper Custom Game scene. The developers have already expressed their wishes to introduce a freely available map editor, so who knows, maybe all of this is just the very first step of a very long plan. Whatever the case may be, the addition of a Server Browser is going to be a great new feature for Overwatch.
On a slight side note, if you're wondering about all of the balance changes that came with this PTR update, you can find them over here. Long story short: Bastion has been reworked and is now actually useful, Mercy and D.Va have received some minor buffs, and there is now an option to adjust Ability Sensitivity so 'Boostio' should hopefully no longer be a thing.