Content from Adobe Stock suddenly downloading painfully slow

Same here. Tried differente browser, different internet connection, but it’s always a pain to download adobe stock assets. I’m thinnking about quitting adobe stock because of this. 

There are some people reporting this, but there are not enough people for this to assume the issue is with Adobe. 

Possible causes and remedies may be:

• the browser and add ons: starting the browser without add ons may help. Clearing cache and cookies may help too, but you've done that.
• using a different browser for testing purposes could be helpful. 
• the firewall may be blocking important addresses. Especially if you are on a corporate network, IT often changes the firewall configuration to update the firewall against known new dangers. That causes sometimes issues with legitime websites.
• The virus checker: as I do not promote traveling the internet without a virus checker, you should do a short test by disabling the checker. Especially third party checkers sometimes create performance issues. That's the reason why I use the Windows build-in protection. 
• Changing the computer may make it easier to detect, if the issue is related to the computer's configuration. You may use any device that uses the same network.
• Chanaging the network (home, work, cell) may help too see if the issue is with the network.
• Some countries throttle the internet. You may test access to stock by using a VPN.

I suggest, you check these points and come back if the issue does not get solved by one or the other possible remedies.

You are welcome to share your solution to this, if you have one. That may help others in the same situation.

Can you try from a different device ?