You asked
Should I switch from the canon eos 6d mark ii to mirrorless?
If your 6D Mark II is doing the job, I wouldn't switch just because mirrorless is newer. The 6D Mark II is a full frame DSLR with a long list of lenses, and that list is the part that keeps it useful. You can see the Canon EOS 6D Mark II page for the full set.
The case for mirrorless is mostly about how you shoot. You see the exposure before you press the shutter, and autofocus can find and follow eyes. The 6D Mark II also has no in-body stabilisation, so you'd be relying on stabilised lenses for slow shutter speeds. If those things are costing you shots, the Canon EOS R5 Mark II is a full frame mirrorless option. Check its lens options before you commit, because the lens list I have for it is limited. Old manual lenses adapt easily to mirrorless, as covered on the Lenses page.
Written by Claude from this site's pages.