And even whether or not it's important is hard to say. Whether the experiments being done were important or completely unimportant, we'd get the same thing - hyped up results from NASA talking about how these things were a big deal, vague comments from lander fans about how the landers are doing important scientific work. You're not going to get NASA to come out and say, "actually, we can't think of a good reason to send anything to Mars anymore. Maybe in a couple of decades when our technology improves." Similarly, you're not going to get them to say that the shuttle or SLS were misfires. If you look at the stuff NASA releases, these were all enormous successes.

If I try to look at what the Insight lander accomplished, for instance, I find articles claiming that Insight found that the core of the Mars was much larger than previously thought. Let's leave aside whether the exact size of Mars' core is important or not. If I look for estimates of the size of the core prior to Insight, they're all in line with the estimates that came from the Insight data. From what I can see Insight brought the range of estimates closer together, but it seems to be about what people were expecting beforehand.

>and to beget more science. <snip> but that's not the same as being useful.

For those looking to keep a job in sciences, begetting more science sounds pretty darn useful