For clarification, this is Vanilla, a performance mod Fabric pack, a Fabric content modpack, Forge modpack, etc. that you are launching? If it’s the modpack that you describe needing 8gb of heap memory allocated, I wouldn’t be surprised the java stack memory taking ~2.7 GiB. If it’s plain vanilla, that memory usage does seem excessive.
Running the same memory constraints on a 1.18 vanilla instance, most of the stack memory allocation largely comes from ramping the render distance from 12 chunks to 32 chunks. The game only uses ~0.7 GiB memory non-heap at a sane render distance in vanilla whereas ~2.0 GiB at 32 chunks. I did forget the the render distance no longer caps out in vanilla at 16 chunks. Far render distances like 32 chunks will naturally balloon the stack memory size.