Discourse works fine and the splash is doing its job. The issue is your theme. I just ran the same test from your other post.
With the theme enabled
https://gtmetrix.com/reports/howtodiscuss.com/Xo3GRFGY/
With the theme disabled
https://gtmetrix.com/reports/howtodiscuss.com/KEzAjPBo/
You have too many ads, and they’re not configured correctly, so they cause the content to move a lot when they load/refresh and make the site unusable.
The ads also cause a lot of CPU/network usage even if your users are just idle on a page. Here’s a recording of 1 minute on your homepage without any user action.