Given the age of the graphics options in Intel-based Macs, the highest end dGPUs in those machines would be miles behind even the most basic modern GPUs in terms of processing power, feature support, etc. Likewise, driver support for those GPUs would be limited at best, most likely at least a couple of years since they were last updated.
Looking at one of the Mac databases, the last Intel Macs with dedicated graphics used either a Radeon Pro 560X or Radeon Pro Vega series iGPU. Comparing the 560x to a previous (to current) generation Radeon RX 6600M, the latter is over 240% faster in aggregate benchmarks. Here is a comparison of those two dGPUs base specs:
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Even the base M1 iGPU outperforms the 560x by around 50%, which means the first Apple Silicon Macs had integrated graphics that beat the dedicated GPUs of the last Intel models. Features such as Ray Tracing, DLSS and FSR were not even available when the 560x was released, and now you are seeing some of those features making their way into the dedicated graphics on Apple Silicon, which just furthers the gap between your Intel-based Mac and current generation machines.