Yes it's possible to come back to the previous icon.
I had the same issue: I really disliked the new icons, they were really ugly.
I tried to search manually on internet for icons that were similar to the previous Microsoft Office, but I didn't found any.
So I thought that to fix my problem I had to come back to the previous version of Microsoft Office...and I found that it is possible!
I found the following youtube video, and by doing everything it shows, it WORKED PERFECTLY!
Before showing you the link that will solve your problem, I suggest to everyone reads this to do the thing that i'm writing now: disable automatic update of Microsoft Office, by entering inside one of the apps of Microsoft Office (ex. Word, Excel...)...once inside the app, click "Account" and then on the right you will find the option to disable "automatic update" of Microsoft Office.
I am suggesting you to do this, in order to avoid the inconvenience that once you will install a previous version of Microsoft Office it doesn't automatically update "back" to the most recent version (that we don't want).
Last thing that I want to tell all of you: the procedure to downgrade the version of Microsoft Office is REALLY SIMPLE, anyone can do this, you dont need to be familiar with informatic...also because the video I am going to write in some lines explains step by step what to do.
So DON'T WORRY.
(One last thing I promise: when you will execute the first code of the video (don't worry it is all explained really easy) it may doesn't show to you all the lines that are shown in the youtube video...don't worry, continue to follow the instructions. Im am telling you this, because in my case when i executed the first code, they didn't appear all the lines showed in the youtube video...I ignored this and continued to follow the steps of the video...and it worked perfectly and exactly as expected).
So here is the video: https://www.youtube.com/watch?v=b2HSjhW6mtI
I wish you good luck, and I hope to have been helpful.