The ‘Site Contents’ page (_layouts/15/viewlsts.aspx) is not user friendly when you have a lot of lists and apps. Make subdivisions for libraries, lists, apps,… like SharePoint 2010. Also remove the tiles. It is too overwhelming.

I should be able to right click on a document in a library and open it in a new browser tab.

Please make this feature available for SharePoint Online.

"For SharePoint Online, the Opening or downloading documents, viewing items in lists, or viewing item properties event is not available."

https://support.office.com/en-us/article/Configure-audit-settings-for-a-site-collection-a9920c97-38c0-44f2-8bcb-4cf1e2ae22d2?CTT=1&CorrelationId=da58a595-60b0-4710-a856-e43640f776f1&ui=en-US&rs=en-US&ad=US

SharePoint supports dragging files from your desktop into a SharePoint document library, but as soon as you want to drag in a folder containing multiple files/sub-folders this is not supported. You have to recreate the folders manually in document library and then drag in files separately, this consumes a lot of time.

You cannot currently load or set the ThemedCssFolderUrl property of the Web object in CSOM. After applying a theme (for example, using the sample PnP code), returning to the app from the newly-themed site shows that the SP.UI chrome control cannot find what it needs to properly display. We need a way to ensure that a new theme that is deployed from the app can set this value so that when returning to the app afterwards the chrome control can continue to display properly.

other CMS systems already allow this functionality. Instead of having to save an image somewhere and then upload it to SharePoint, let me just drag / drop images on the wiki and blog pages. Would be ideal for screenshots

Make it easier to move documents between folders. It is now possible to use drag & drop to move to sub folders but there are no easy way to move documents up in the structure.

I heard that in SharePoint 2016 there was NOT going to be any SharePoint Designer! PLEASE! I use it almost daily to provide simple workflows such as email to colleagues and other options that "Out of the Box" functionality can not allow and where InfoPath does not provide "If Then" statements for the ability to create Calendar items if conditions are met.

Please change how SharePoint generates links to uploaded documents and site pages, so that URLs with spaces will replace %20 with a dash instead. Most CMS tools including blogs do when generating SEO friendly URLs. Links with %20 throughout are too difficult to read.

This feedback site is a perfect example:

This:
https://sharepoint.uservoice.com/forums/282887-customer-feedback-for-sharepoint-server

is easier to read than this:
https://sharepoint.uservoice.com/forums/282887%20customer%20feedback%20for%20sharepoint%20server

Please make the "(+) new document" button from the web part and document libraries match available CTs as the ones available under the "New" button from the Ribbon. Please also include "Document sets" in the available CTs :)

You guys really ought to license the Office Web apps as part of SharePoint without needing to setup individual user licenses. My company just moved over our intranet to SharePoint and I tried editing a spreadsheet in the browser from a computer that does not have a modern version of Excel installed and it says Web apps is not licensed. You are bundling web apps with OneDrive and with your Office365 subscribers. SharePoint is already expensive enough to not include this for free.

Upload via Drag&Drop is very easy but it is hard to set the metadata this way.
you need 3 clicks - no user does this much work to set metadata

The breadcrumb becomes fairly useless after you have arrived at Document Library level. Folders are still a very important way for users to organize documents. Once you start going into folders, there is no telling from the navigation controls where you are.
This could easily be fixed with an improved breadcrumb which shows the path down to the folder level.

Ideally this should even be an option that you can control from navigation settings, which currently allow zero control over the breadcrumb control.
This is something you should be able to manipulate through configuration without the need for custom code.

So Infopath 2013 is supported in 2016, but SharePoint really needs a full modern full-featured forms editor. FoSL looks promising but the functionality is not clear at this time.

The sync limit does not match OneDrive for Business, and adds complexity to the end user experience, administration and architecture of SharePoint. Please remove this sync limit.

The 'Navigate Up' button on the library ribbon tab is too hidden for users and it also requires an extra click every time you need to go up. The breadcrumb also requires an extra click because you have to click the 'Browse' tab in the ribbon to see it every time.

Current term set based solution is not usable at all in real life multi site collection scenarios.

The mobile views are not a solution, so many customers turn to custom design, but I would rather a responsive design be built into SharePoint.