Dell S3423DWC (USB-C)

So I've just upgraded to an 34" ultrawide Dell S3423DWC, having used a Dell U2520D USB-C for display + charging for the last two years with my 2017 Macbook Pro without issue.

Sadly on connecting my MBP to the new display, the USB immediately shuts off and MacOS shows a warning the "USB Accessories Disabled - Unplug the accessory using too much power to re-enable the USB devices." error. I can use the same cable as I was using previously on two other USB-C Thunderbolt non-apple laptops without any error. The error itself doesn't make much sense because the monitor supplies power TO the laptop, not the other way around. 🥺🤷🏻‍♂️

Any ideas?! I'm really not interested in buying a hub or usb-c / dp / pd capable adaptor... USB-C and PD is a standard, both vendors should be implementing correctly per the standard.