external monitor refresh rate will not go higher than 30hertz

I connected a Dell P2715QT 27" 4K Ultra HD IPS LED Monitor to my 2021 16" macbook pro via an hdmi cable capable of 8k. When I try to adjust the frame rate through system preferences > displays> display settings> select the screen I'm adjusting (Dell), click refresh rate, the highest rate is still 30 hz. The lag and jumpiness on the dell monitor is very noticeable compared to the very smooth movement on my macbook screen. I thought the 8k hdmi cable would solve the problem, however the refresh rate options for the dell monitor still shows 30hz as the highest rate available. Does anyone know how to fix this?

Is it possible the 8k hdmi cable is overkill and I specifically need a 4k cable?

Additional info: the dell monitor only has 1 hdmi port, I couldn't find any relevant settings while navigating the monitor's screen settings, I first tried using a High Speed w/ ethernet hdmi cable which showed the same refresh rate - I was certain the 8k cable would fix it but it made no difference.

thanks!