No - this is good research, it just isn't "magical slam dunk science" many are conditioned to expect from years of watching CSI.
Tightly controlled studies involving humans are *very* expensive and *very* difficult to control the logistics of. The purpose of the study is to examine if there is a reasonable possibility of a link - and if so it would justify more detailed, controlled studies. That's how actual science works, you build up the research and multiple groups look at it from multiple angles, you don't solve a problem in one "magical" paper.
was the heart failure related to takeout *containers* or to the type of *food* that is typically put into takeout containers?
The study finds that some connection exists - it might well be the type of food, or how the food was prepared, but that's something you address after the initial connection is shown, from this sort of paper.
Who boils takeout containers...
Affectively - many restaurants. Hot food from the kitchen is placed directly in containers, then bagged and put in thermal bags for delivery. Boiling in this instance is a simple mechanism to replicate the affect, and see if dosage increases over time. The researchers show this impacts the rat gut biome. This justified looking at the problem in more complex species and a variety of heating methods.
Who exclusively drinks water boiled in takeout containers?
The point is to show a simple transfer mechanism - heating water in the container - is sufficient to impact the rat gut biome. This shows us it isn't dependent on oils or other materials from cooking process, hot water alone is sufficient. This is textbook good science - they have eliminated confounds despite your claims to the contrary.