I can empathize, though my lack of a taxable investment account wasn't due to any particular market fears; rather, it was due to wanting to avoid the additional complexity if possible. When I embraced the desire to FIRE, and stopped mentally separating my 'non-retirement' and 'retirement' assets, it became clear that I needed to throw a bunch of money into taxable equity investments.
Make sure you take advantage of tax-loss harvesting. I know that it might seem counterintuitive to want to sell when you've lost money, but that's the way the tax code works. If you don't know how to do it, ask some questions.