Yikes. As a huge fan of the first three movies, I had to chime in. This one makes Collision Course look phenomenal. I'm uncertain about production details (whether they had a lower budget, if they were rushed, or had an entirely new writing team), but I can say at face value, this film is without a doubt the worst one of the franchise.
A couple of good things - the impressionists for Sid and Diego were alright. It is genuinely difficult to do a good impression of Ray Romano, so I was forgiving of that.
But - the pacing was poor, the voice acting (and honestly, the design) of the villain was strange and underwhelming, the environments were overly simple, the movements of the characters were uncomfortably static, the shot composition was unbelievably plain, and seemingly, all the characters established throughout the franchise were...forgotten?
I absolutely loved Buck in the third movie, but somehow, in spite of Simon Pegg's return, he was bland and uninteresting.
I normally don't leave reviews, but it feels fair in this case, as Disney has taken hold of a relatively unique property and spit out something on par with the infamous "straight to DVD" Disney sequels. It seems that little care was given, as I imagine Disney DOES have the resources to produce something with slight personality, rather than what felt like fan-fiction.
Nothing against the team who made the film - but I am against those in charge who seemingly put up barriers to prevent the team from creating something artistic.