This is not always the case. If you pop in a much stronger GPU, the CPU will still be the same, and can only send pre-rendered frames as fast as it can. Getting a new GPU with the CPU remaining the same does not produce results, where you get a huge benefit. The GPU will always be waiting on data from the CPU, and will sit at low usage even when gaming. Not ideal.
TBH, the OP needs to consider a new build.
Something like this to get started. It will dance all over the current specs. Drop in a dGPU down the line when money is saved.
PCPartPicker Part List
CPU: AMD Ryzen 7 5700G 3.8 GHz 8-Core Processor ($181.83 @ Amazon)
CPU Cooler: Thermalright Peerless Assassin 120 SE 66.17 CFM CPU Cooler ($33.90 @ Amazon)
Motherboard: MSI B550 GAMING GEN3 ATX AM4 Motherboard ($99.00 @ MSI)
Memory: Corsair Vengeance LPX 16 GB (2 x 8 GB) DDR4-3200 CL16 Memory ($39.99 @ Amazon)
Storage: Kingston NV2 1 TB M.2-2280 PCIe 4.0 X4 NVME Solid State Drive ($60.99 @ Amazon)
Case: Lian Li LANCOOL 216 ATX Mid Tower Case ($99.99 @ Amazon)
Power Supply: Corsair CX650M (2021) 650 W 80+ Bronze Certified Semi-modular ATX Power Supply ($69.99 @ Best Buy)
Total: $585.69
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2024-04-15 11:11 EDT-0400
I would not throw any money at that older system. It's simply not worth it.
This is a full build. Depending on what PSU, Storage etc, this bill could be reduced.