Maybe I'm a minority, but I can't really trust anything from a company with a login screen that says "logging you in securely" for 5000ms before loading me (sometimes) to my dashboard.
I agree with you. This is one of my biggest pet peeves. But we're working hard on load times. Every call is HTTPS, adds lag. But you'll start to see improvements on the new experiences that will start rolling out in Q1. One thing after another, we're improving the company, its platform, and its engineering culture. I have to say I'm quite proud of the team behind Kraken. This framework is solid.
In all seriousness, adding interstitials can provide value. If the login performance has high variance, it's better to set an expectation that it will take 5 seconds than leave the user wondering if the click actually worked. Similarly, Apple has done an amazing job with UI transitions in iOS to mask the actual load time.