Day-to-day comparisons show Cars 3 and Transformers 5 trailing their predecssors in the US (the latter by a very wide margin), neither likely to make $200 million domestically, just like Pirates 5. Pirates 5 will also probably make $200 million less at the foreign box office than the last one and Despicable Me 3 just opened in the US with a total lower than 2. This does not get into how GotG2 made less than Disney hoped,
Wow, the goalposts moved so fast in this paragraph that I got whiplash!
But, in earnest, if you're going to make the point that sequels make less money and then list a bunch of examples, you can not include GotG Vol 2. It made more money than Vol 1. Saying that it made less than what was hoped is not the same thing as making less.