Premiere Pro not utilizing GPU/CPU

I second Ann. You're doing both upscaling and re-rendering at a different frame rate than what your source footage was to begin with. And that processing eats up your system RAM, and to a lesser extent your CPU.

Your Radeon RX 5600 XT, on the other hand, does have hardware H.264 and HEVC encoding albeit only with 4:2:0 chroma subsampling (as it is based on the first-gen RDNA architecture from 2019).

What all this means is that you definitely need a new CPU platform in your PC since even if you do upgrade your RAM in your current setup to its maximum supported amount of 64 GB, your current CPU would then become the new bottleneck to your workflow. Plus, the most powerful CPU that you could have upgraded to, the i7-7700K in your case, will have all servicing and support completely ended by Intel itself in a little over one month (not to mention that it would not have been a worthwhile enough upgrade from your i7-6700 to justify your continued use of that now-almost-9-year-old CPU platform).

Under the circumstances, save up your money and put it towards a new CPU, motherboard and RAM. And only then it would be worth upgrading to a more powerful GPU (which may also necessitate a new power supply unit as well).

By the way, while you're at it, I would also discontinue utilizing your current workflow since no software upscaler performs high quality upscaling. The only quality upscaling solution is an astronomically expensive dedicated hardware upscaler that does not depend on a PC to do its job. Every single software upscaler degrades image quality to some degree. The worst ones degrade your 1080p original when upscaling to "4k" to the point that it looks almost as bad as an average 480p video!

You are trying to upscale from HD to UHD and changing framerate which is CPU intensive.

The gpu wont do anything much in this case.

On a side note the upscaling will cause image quality loss.

That's due to your sequence, your export codec, your CPU, and your GPU.

First, that is an ancient CPU ... from 2015. Only four cores, hasn't been any updates even for it since 2022. It does have QuickSync, but the early low-powered CPUs with QuickSync weren't that much speedier at doing the job of H.264 encoding than the CPUs without.

I don't know what the clip on the sequence is, but you're exporting to H.264 ... a long-GOP format ... and that CPU is maxing out just handling that.

Then your RAM is rather small for Pr2024 ... 16GB is barely enough for Premiere to function. Not for it to race along. And hopefully you've got a LARGE cache space on a fast internal SSD like an Nvme slot, though ... doubtful ... 

I don't think that GPU can do anything with long-GOP H.264/5 encoding. AMD has finally added that to some GPUs of their latest generation, but it doesn't have the stuff to do any H.264 basic encoding.

And that export, going to  H.264, is of course ... crucial to the problem. Other formats might get done faster.

Next ... Premiere does not use the GPU as "just additional CPU processing" ... it's a very specific, different usage. Check out the "GPU Accelerated Effects LIst" ... as the GPU is used only for things on that list, like Warp, most color things like Lumetri, some other effects. So Premiere will use the GPU when it has GPU stuff to do.