You are fighting the wrong battle. You harp on the technology used rather than the specific functionality you desire.

The bad way to do it: "You made a single page app with PHP and {other tech} and {database}! I hate those! Don't you read (reddit, twitter, hacker news)? Best practices say..."

The good way to do it: "Our users often share links within the application with each other to navigate and the new single page app you demoed doesn't allow that."

Or: "While the page load times look great on the metrics in your power point, as everything is lazy loaded it takes 10 seconds for the page to actual become usable, the old site loaded in under a second why are we regressing the user experience here?"

Or the evergreen: "What does that buy us?"