What you’re talking about is called lazy loading. It loads text first and CSS and then images after.
Most modern sites now do this along with needing to load it at all until you hit the continue button. That not only reduces your browser load, it also reduces server load as well.
There are many other reasons to have the continue button, but the positives outweigh the negative. It’s not considered a dark pattern and helps the content team improve on their content.