It's great that you have this many years of experience. It's all about coming up with unique or innovative ways to get new opportunities and to start a business where it would work for you in the long run. I'd suggest a few things:
1. You can create a website with your portfolio and build up your online presence through on-page and off-page SEO.
2. Create an innovative style for your personal brand and this can be in the form of video reels.
3. If you'd like to sell a "product" using your skillset, you have to identify what it is that you'd see yourself passionate about even after 5 years. In this case where you have 15 years in the design industry, you can offer online courses in designing.
4. Use Pinterest, IG, and Tiktok to get new opportunities and organic traffic
5. Research is Key, even cold calling still works but you have to identify your prospect, pitching to everyone will not work.
6. Youtube, Tiktok, and even Pinterest have many resources to help you come up with new business ideas and also show you how to accomplish them.
7. Fiverr, Upwork, Toptal, Designhill, Peopleperhour and many more sites are a great place for you to find projects. Check out my blog post on this it will help you a bunch https://virtualbossmindset.com/12-best-place-to-find-freelance-graphic-design-work/
If you need any assistance with how to start a profitable business, schedule a time to chat with me.