Now, while this is frustrating, lemme tell some of the younger people here a horror story. Fair warning: if you didn't get onto the internet until the early 2000s, you might not be able to sleep after reading this.
Once upon a time... The internet was always this slow to load. Everywhere. Every page. Every image. Even porn download (and we didn't even have HD yet). Every song. And if the phone company/ISP was nice enough to accidentally publish your dedicated 56K dial-up line like GOD DAMN IDIOTS every telemarketer call that connected would knock you offline and you'd have to spend upwards of 5 minutes reconnecting sometimes and start over loading a page again. Back in the days of Limewire, Kazaa, ect. I remember taking the better part of a full day to download some movies (that were SD and often filmed with a potato that had recording features with half the screen out of frame and people walking in front of it) and I thought that was blazing fast back then.
I kinda find it difficult to believe that Mangadex is always slow including ridiculous what-should-be lower use times (It's 12:30 AM here on the East Coast of America and it's like ~6 AM or earlier in Europe - how the fuck could there be that many people browsing to slow down the server THIS DAMN MUCH?), but, not much can be done on our end unless we all donate a shitload of money to update the servers... which will take time to implement even if we did.