I'm in two minds about this. In favour: TTI and similar metrics are really important, not just for SEO but because Google and friends base these metrics off ac

I'm in two minds about this. In favour: TTI and similar metrics are really important, not just for SEO but because Google and friends base these metrics off actual user behaviour: if your page takes to long to load, users will go elsewhere. Lazy-loading for features that are rarely used (and you've actually done the analytics to justify this) can be a valid trade-off. Against: this behaviour in some form has made it even into Microsoft Word. Click the "select font" dropdown and it can freeze for a couple of seconds to create the list, especially if you have a big document open. The same, if you're unlucky, for the styles dropdown, the "insert special character" button because it insists on showing you the most-recently-used ones in a menu it has to build on click (as well as in the dialog box), and a few other places. I expect better than this from a desktop application, especially as I remember these things being almost instant back around WinXP days. Sure it didn't come with Bing integration, but I can live without that. And web sites and applications should aim to emulate the responsiveness that we used to have on the desktop.