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.
I started my career in SEO and moved into web Manager because it was just too tiring keeping up with Google. I think my last update that I could remember was called "Panda". This is when they named their updates.
My current SEO strategy is super simple. Have the content you're writing for relate as much as possible to the user intent. Give the user what they are looking for FAST and then crosslink, cross sell after. You will have a good page.