I have seen several discussions similar to this, but nothing the same as what I am experiencing. So I thought I should add the following to the conversation.
We host several databases using FM Server 15 on a Mac mini Server (Late 2012) with 16GB RAM running macOS Sierra. On the same in-house wired network, I am running FMP 15 Advanced with File Cache set to 128MB on an iMac (Late 2012) with 8GB RAM running macOS High Sierra. All versions of macOS and FileMaker mentioned here are the latest available.
Making changes to my databases is fairly seamless with this setup - taking virtually no time to access the Manage Database screen, change the View By setting, Duplicate a field, Change a field name, or Delete a field; and as little as a few seconds (though sometimes longer, depending on how many and how complex the changes are) to save any changes made by clicking OK to close Manage Database.
Testing newer versions of FileMaker for deployment, I get very different results trying the same things on the same hosted databases while running FMP 16 Advanced and FMP 17 Advanced on the iMac, both with File Cache also set to 128MB. Simply opening Manage Database takes 60 seconds, as does closing Manage Database after making changes. And each one of the other operations mentioned above takes roughly 30 seconds to complete.
Deleting the caches (~/Library/Caches/FileMaker/DBCache/) on the iMac had no effect.
Is this related to the other slowness issues I've seen, the root cause of which have not been addressed as of FM 17? Or is this issue different enough that there may be a solution I can try (short of upgrading the hardware or software indicated)?