I'm running a site with 90+ plugins active (don't ask) but there is literally only one that causes small issues. I'm not saying that WPEngine is lying or anything, but not having the OPTION to turn on PHP7 has pretty big consequences for a few of my clients. Simply because they have a heavy stack of plugins (WooCommerce, Membership Plugins + BuddyPress, Jetpack) the performance of WPEngine hosted sites compared to other hosts becomes very noticeable. Especially because as a developer I'm unable to use Redis or Memcached for logged in users I have no options to improve site performance. This has been incredibly frustrating for a while now, and I've stopped recommending WPEngine to clients that want more than just a regular blog.