Viewer folder whitelisting is a very effective 'fix' for slow texture/mesh loads (doubly so if you use a TPV). If you don't whitelist, every file that gets written to your cache gets scanned by your AV suite, which is minor if it's just one or two, but when a sim has hundreds or even thousands of textures (nevermind what any avatars bring with them), that's a lot of processor cycles wasted.

This also brings up the idea of 'pre-visits'. If you've never been to a sim before, you'll have to load it when you go there the first time. The same goes for when you haven't visited in a while - the elements will likely be expired in cache if they're even present at all. So if you want to get decent performance while visiting a sim... show up early, give your viewer a chance to get everything in cache.

And then there's the "techie" fix - where is your cache? what kind of drive is it being written to? Older systems with physical drives will be noticeably slower than those with m.2 PCIe or even SATA solid-state storage. So IF you've installed your viewer to a slow drive, consider reinstalling it to a fast one. If you can't do that for reasons, you can also redirect just the cache folders to another drive. You want to choose something that can handle a lot of reads and writes, but for smaller files. External drives are slow, and RAID arrays can also slow things down.

Another source of file write delays are mirrored folders. Services like iCloud or OneDrive will latch onto 'important' system folders, like Documents, Pictures and so on, and they will copy every file that gets written or changed. Not only does this delay things with your processor doing extra work, but your net bandwidth gets hit, cos you're uploading everything that gets streamed to your system. Since most people's net connections are asynchronous (big download bandwidth, itty bitty upload pipe), you can easily max the upload and now you've a queue... which slows things down really bad. So make sure that your viewer's cache location is NOT in some subfolder that OneDrive thinks is important and needs to be mirrored to the cloud.

I confirm this experience. It sometimes takes up to three minutes for textures to fully load. (Apple Mac M1)

Window-Paths are less helpful ;-) Not sure, if it is really a Whitelist Issue.

There are several reasons for this, limited data reception (ie broadband), your computer specs, anti-virus scan because SL is not whitelisted, time of day(some providers throttle when high demand), bad RAM, registry full off garbage, HD a mess or failing. A few more, but white listing if you have anti-virus is a start.

Try whitelisting the cache folders in your antivirus. that solved the problem for me.