Is there an objective answer to whether or not taking a multi-vitamin dietary supplement is beneficial to health?
No, there is not.
If you dig into the existing research, unless you are looking to experience some confirmation bias one way or the other, you will only continue to find evidence that there is no conclusion.
In this case Wikipedia actually does sum it up nicely, emphasis mine:
Provided that precautions are taken (such as adjusting the vitamin amounts to what is believed to be appropriate for children, pregnant women or people with certain medical conditions), multivitamin intake is generally safe, but research is still ongoing with regard to what health effects multivitamins have.
Evidence of health effects of multivitamins comes largely from prospective cohort studies which evaluate health differences between groups that take multivitamins and groups that do not. Correlations between multivitamin intake and health found by such studies may not result from multivitamins themselves, but may reflect underlying characteristics of multivitamin-takers. For example, it has been suggested that multivitamin-takers may, overall, have more underlying diseases (making multivitamins appear as less beneficial in prospective cohort studies). On the other hand, it has also been suggested that multivitamin users may, overall, be more health-conscious (making multivitamins appear as more beneficial in prospective cohort studies). Randomized controlled studies have been encouraged to address this uncertainty.
I'd love to quote the whole "Research" section here, but if you read through it, and between the lines, you can start to get an inkling of just how all over the place and inconclusive research has been.
For example, the citation for the "randomized controlled studies have been encouraged" bit is simply a paper from 2011 that concludes with "these results highlight the need for more case-control studies or randomized controlled clinical trials to further examine this relationship." In other words, as recently as 5 years ago, at least one researcher was still in the state of realizing that randomized trials may be needed to clear things up.
Every credible source, e.g. Johns Hopkins, periodically releases some article that says "In a recent study, vitamins have shown to be beneficial / unhelpful". If you dig into the methods of these studies you will likely find (very reasonable) initial bias in both directions as well as the introduction of other variables due to the selected sample set.
For example, the title of that that Johns Hopkins editorial linked to in the other answer is "Enough Is Enough: Stop Wasting Money on Vitamin and Mineral Supplements". With a title like that I'm sure that research wasn't neutral to begin with (not that it was bad, it's just this is a really inconclusive topic so it's easy to interpret study results according to initial views, hence the fact that this has been an ongoing conflict for decades).
The abstract of that study concludes with the absurdly inconclusive, and probably biased, "Although available evidence does not rule out small benefits or harms or large benefits or harms in a small subgroup of the population, we believe that the case is closed— supplementing the diet of well-nourished adults with (most) mineral or vitamin supplements has no clear benefit and might even be harmful." -- A sentence which I can't help but laugh at because, you know, what? -- The issue really is so up in the air that anybody can pretty much find any data to support any viewpoint. You can pick anything you want from that abstract and use it as a basis to publish an article with a catchy headline like "The Vitamin Verdict" that supports your view either way, there is very little objectivity involved.
However, there does at least seem to be a general consensus that, massive overdose aside they don't hurt (except for the couple of studies that said they do, which were countered by meta studies that said the studies said they didn't, and so on...).
Note by the way this isn't really "of late", well, at least not in the US where it's been a slowly but steadily increasing trend for at least 30 years. I distinctly remember having a heated conversation with somebody about this exact same topic 20 years ago.
I think personal dietary and health trends are simply too varied to make any kind of general conclusion here. Perhaps they are good for some people in some situations and have no benefit for others, and every study from now until the end of time will continue to be inconclusive and unintentionally (or intentionally!) biased.