We can agree to disagree Taiwan belongs to China whether you believe its ROC or PRC but it belongs to China. Taiwan didn't belong to the Dutch they were just allowed to stay since they couldnt stay in the mainland during the ming dynasty. Ming was more concentrated on the threat to the north of the Manchu so didn't pay too much attention to the seas. Dutch just took advantage due to the ming-qing war. They had no claims they were thousands of miles away from their home base.
It's not a done deal. When diplomacy fails you use cold steel or in this case bombs and bullets. I just wish the mainland government have balls to take it by force perhaps maybe when they have a stronger military and do not fear the United States.
It doesn't concern me because I'm chinese American but i'd hate for the motherland to be splintered and divided which every Chinese agrees. Taiwan is coming home whether in 20 years, 50 years. It's a long shot but I hope one day China can break out of the encirclement and reclaim Hedgemony in the region.