That's a bit misleading. There's several tools you have available and you should pick the best tool for the job. Also, SPAs are only harder if you haven't already learned them. For anything too complex to not simply use WordPress, it's often preferable to use an SPA for the superior UI/UX experience (both for the developers and the user). Plenty of exceptions are welcome though, for example if the site's functionality is based around a key jQuery plugin.