The default templates on Google Slides suck. Check out this great free site with beautifully designed templates! None of my colleagues had heard of it, so perhaps you'll find it useful too :
Green Doodles. Free PowerPoint Template & Google Slides Theme
Slides Carnival Category Free Templates PPT Slide
Google Slides and PowerPoint for Carnival Presentation
Clean Minimal. Free PowerPoint Template & Google Slides Theme
Cool Circles. Free PowerPoint Template & Google Slides Theme
6 Easy Tricks for Designing Text-Heavy PowerPoint Slides That Won't Bore Your Audience – SlidesCarnival
Free Tech PPT Templates – SlidesCarnival
Clean Minimal. Free PowerPoint Template & Google Slides Theme
Colorful Light Bulbs. Free PowerPoint Template and Google Slides Theme.
Professional Business. Free PowerPoint Template & Google Slides Theme
Amusing Carnival PowerPoint Template and Google Slides
SlidesCarnival: Free PowerPoint & Google Slides Templates That Stand Out
How to Make a Compelling Business Plan Presentation: Tips and Free Templates – SlidesCarnival
Simple Corporate. Free PowerPoint Template & Google Slides Theme
SlidesCarnival: Free PowerPoint & Google Slides Templates That Stand Out