The question just is: Is the delay caused by the core ST or by an plugin, which takes too long to return control to ST?
To figure that out, you need to prevent all plugins from loading. If the issue persists, the culprit is ST, if not a plugin is causing it.
In the former case the core devs may need to have a look.
In the latter case, you’d need to find out which plugin is the culprit to file an issue at the plugin’s github repository then with as many information about your setup and file locations as possible to hopefully enable the author to find the reason.
I woudn’t recommend to destroy your setup by deleting the plugins, but just to temporarily rename the data directory so ST thinks it’s running the first time.
The painful part is finding the plugin, which causes your delay then. Most likely a completion provider or a plugin used to manipulate or analyze the text.