Being the sole designer in a company can be tricky, and you may miss the valuable feedback and the back-and-forth of ideas that comes from working with other designers. But there are still options — you can teach your non-design coworkers to provide better feedback, and you can find outside community to help validate your ideas.
1. Teach non-design coworkers to provide design critique.
If you show your work to your coworkers, they'll probably have feedback, even if they don't know how to articulate it in design terms. Teach your coworkers how design critique works, and give them examples of the kinds of feedback that are helpful. Teach them to frame feedback as descriptions, not prescriptions ("how can we accentuate the logo" rather than "make the logo bigger").
2. Be part of a design community.
Join an outside community of designers that can provide feedback for each other. This may be online (like a regional design Slack team), or offline (a gathering of designers who are willing to provide each other with feedback). If this doesn't exist near you, start it!