My template opens up with everything disabled, so in my case I don’t think it has anything to do with a specific plugin. They are mostly Kontakt anyway....On windows 10 as well....and I can confirm in my case it loads probably 75% slower and close times can take over 10 minutes when it usually is less than a minute on VE PRO 6. This has been reported in detail to them with very little response. Judging from another users post on Vienna's site I do think it has to do with certain instruments and even more specifically maybe certain kinds of patches in instruments.
In my case I identified that I use a tremendous amount of HALion 6 and HALion Sonic SE instances, and when the patches utilize a convolution effect (either the convolution reverb or the amp vst which is convolution based) the initial connect time is very long only the first time then it behaves as normal. I thought this might be a Steinberg specific issue but last week this behaviour was reported by someone who does not use any HALion instruments. So it is possible that this is all related to the issues I am seeing in VE PRO 7.