Is a stock worthless if delisted?

Is a stock really worthless once it's delisted from a major exchange? Is it a sign of total failure, or could there still be hidden gems amidst the rubble? Could investors still salvage some value from these delisted stocks, or should they be avoided like the plague? How does delisting actually affect the underlying company? Does it automatically mean bankruptcy or can the company still turn things around? What are the potential risks and rewards of investing in delisted stocks? And finally, what factors should investors consider when evaluating these potentially high-risk, high-reward opportunities?