Scheduling algorithms must be used on the radio side of these technologies in order to map radio sources to incoming/outgoing data packets and satisfy quality of service requirements such as latency and error rate. But are they also used in core network components such as SGW/PGW or UPF for reasons such as delivering latency sensitive data sooner to the radio side? Would scheduling packets in core network side be meaningless since they will be scheduled again in the radio side?
For the most part, the scheduling happens in the eNodeBs (gNBs in 5G). Core network components may use "scheduling", as part of the QoS mechanisms to meet end-to-end latency requirements, etc., but that is different from scheduling over the air that happens in eNodeBs (gNBs) and that takes into account the channel conditions, interference conditions, etc., that are radio related and the core network components have no knowledge about.
Having said that, we cannot say that "scheduling packets in core network side" is "meaningless". As the core network components are still concerned about the network latency. They would do their best based on what they know, which is the QoS parameters like QCI (or QFI in 5G) that they see in the packets, as well as the traffic flows that they have been experiencing, and so on.
The radio components and the core network components each do their part to support goals like end-to-end latency, based on the knowledge that they each have.