Minecraft loads chunks very slowly even on SSD

I clean installed Minecraft and tried to make a world. It starts saying "Building terrain" for about 30 seconds, then gets stuck on "Downloading terrain". The RAM usage goes to about 1300 MB during this process. I then finally get into the freshly generated world, but everything is all blue. I look around with a nice 200FPS, but I'm just falling into the void.

Before this, Minecraft would generate the world at a considerably fast speed, but hang when generating chunks very badly.

I have it running on my new SSD with an i7, R9 290 and 24GB RAM, so I don't think it's my hardware... I tried with Optifine, and without, both cause the same result.

This is all singleplayer.

Try getting Optifine and turning optimization features on. If that doesn't work or won't work, try allocating more RAM. To do that, in the launcher go to edit profile. In there, check JVM arguments and there will be probably -Xmx1G in it. Change the number to allocate more RAM.