I don't think there is anything wrong with AMD sticking to PCI-E 3.0. The fastest mobile GPU now is slower than a desktop version of the RTX 3070, which is not going to saturate PCI-E 3.0. In addition, I don't think laptops are suited for PCI-E 4.0 SSD as well because they run very hot without proper cooling.
Based on my experience with AMD and Intel laptops of late, I don't think there is anything significantly lacking from AMD. If any deficiencies, it is mostly due to AMD processors being used in lower end laptop models which ends up with poor components such as battery, monitors, etc. In fact, I will go to say that AMD really pushed the boundaries by releasing 8 core mobile CPUs while Intel is still happy to milk their customers with 4 cores. I am still using a Ice Lake U based laptop, so not bashing Intel without reason.