Yes you can reach the developers directly.
We all knew that SharePoint online will be fast, better, will have new features deployed more rapidly than the on premise world , but what happened in the last weeks, months changed dramatically how the product looks, works , reacts. While this is simply mind blowing , the high number of new things to discover can sometimes be tiresome. Finding your way around the new UI, changing the way one used to do things to adapt to the changes, even signaling issues can be sometimes difficult.
For this, I believe I cannot stress hard enough how important it is for the customers to be able to reach the product team as seamless as possible, ask questions, submit new ides to improve the features, send thoughts and feedback. This need was already raised multiple times by you , our customers and it was heard.
What you will notice , for each new UI experience, in the lower part of the screen, a new button was added: "Feedback". Based on your experience, you might probably think of it as a "send us something , we'll have a look whenever we find time".
Well , you would be WRONG.
The New and Improved Feedback Button :) facilitates a direct connection between you and the feature team. Clicking the button will send an email with your message to the team and, should you select that you want to be contacted by email, you will be.
Now, particular to the new document library UI change and Sharepoint Home (if you missed it , have here a look), clicking the Feedback button will open a new post on https://sharepoint.uservoice.com and this will be directly answered by the product team.
You were asked to "check it out", we won't know if you did (and how you feel about it) until you tell us.
By all means, DO USE the New and Improved Feedback Button, or go directly to https://sharepoint.uservoice.com and send us your thoughts, ideas , suggestions, issues, feedback.
P.S. How to enable the Document Library UI ?