Things that work: All Android phones, Macbook, System76 Laptop, Sony Headphones, JBL BT Speaker, some cheap-o tiny RC car.

All devices don't need to implement everything, I'm happy just being able to bring one charger, one powerbank and a couple of cables with me along with my devices. I was on a trip just the other day where I brought the powerful Apple charger I have, my Xiaomi powerbank, Phone, Speaker, Headphones and laptop.

I'd say this is a lot better than how it was not too many years ago, so I'd say they've succeeded.

My guess is that the Nitecore works with the RPI charger because it doesn't actually negotiate anything, just deliver a voltage on the power-pins. Your Nitecore gear is to blame for the trouble you're experiencing, I'd still say having one "smart" usb-c and one "stupid" is better than everyone having their own physical interface.

It's a really tiny one, with a one cell battery. The problem you'll experience looking for USB-C to charge your RC is that it's not "possible" (You'll need a charging controller on your car instead) since the batteries are usually more than one cell and therefore needs balancing and such. Also when you're charging you're allowing currents up to 5 amps in most common chargers, when I'm in a hurry mine goes to 20 amps, this is above what USB-C is rated for, so you'd have to negotiate the latest 200+w power, transform it to the right voltage etc...

I recommend you give that one up for now, sadly.

Just wish there was something you could plug into an existing charger and go

That'd be my recommendation, my father happens to be a reseller so I've got some know-how :)