Most patents are probably not valid, and most patents used in licensing offers / threats are probably not strong enough to avoid being invalidated or found not infringed if litigated, but the would-be licensor / troll counts on the threatened party to settle rather than pay millions of dollars for litigation.

While there aren't any easy tactical solutions and a policy fix is a dim hope, we should be able to at least partly solve the problem by training an AI to do automated and thorough prior art search and analysis relevant to a patent, so a lot of the legwork of a patent litigation threat becomes orders of magnitude faster and cheaper, and it becomes vastly easier and less intimidating for a trolling target to respond to a patent threat like this, and quickly get their focus and resources back to developing their technology. Software eats patent attorneys, and reduces the burden of patents on the technology community.

(disclaimers: I am a patent attorney and I'm currently working full-time on coding a patent search & analysis AI service, this is not legal advice, etc.)