OK, that's fair enough. But to my mind, this is just a setup that cries out for an explanation that never comes. It's a major flaw in the dramatic structure of the narrative, a bug not a feature.
But I guess we'll just have to agree to disagree about that.
As a kid first reading it, I feared the barrow wights as much if not more than the Nazgul.
The whole aside was to show that the hobbits had truly "left the Shire" and that perils lay along the road in any direction they might turn. But, again, there were allies or, at least, guides all along that road as well.
Bombadil and Old Man Willow are a foreshadowing of the Ents to come.
OK, but Tom doesn't strike me as particularly perilous. He just seems weird.
Does that answer your question?
Ha! Yeah. At least you're consistent :-)
Lynch fills his works with characters and scenes that are—at best—plot-adjacent, whimsical/incongruous/uncanny, and full of often-unexplained and apparently-metaphysical mystery or magic. He's as likely to let mood or theme drive the content of and editorial-decision-to-include a scene or a shot or an entire character(!), as plot. It makes sense you'd dislike his stuff if you don't like the Bombadil section of LOTR.
(this is not intended as some kind of judgement, to be clear, I was just curious if works with similar qualities had the same effect for you, or it was something specific to that kind of element being in LOTR in particular, maybe because of the context or something)
LOTR is mostly like that. Most of the events make sense in the context of the overall arc of the narrative. If you ask, "Why is this scene here?" there is usually an answer.
Except Tom. He appears, puts on the ring, fails to disappear -- which is quite extraordinary! --- and that's it. The end. Toodle-oo. Vanishes entirely from the story without so much as a by-your-leave. Why was he introduced? To this day I have no idea. And that is why Tom bothers me particularly. With Lynch you know what you're getting. Tom seems like a bit of a bait-and-switch.
As others have also stated, Tom is one of my favorite characters purely because he is left so unexplained. Tolkien sought to create a world. In order to create a world [0], it doesn't make sense for the whole of that world to be defined by a singular story or set of events. Least of all a world created by an author who so dearly loved folklore and mythology.
[0] an interesting one, anyway.
You could go on to explain that fact or similar, but I think driving home that point any more than Tolkien did just muddies it and makes it more clumsy.
One of Tolkien's goals was to create something which resembled history rather than literature. Or if not history, then mythology that plausibly belongs to a real place, rather than a neatly-constructed story. So, some of the things that he does are "janky" from a purely dramatic perspective, but fulfill that purpose.
A common example from Lord of the Rings is having many related characters with the same or similar name. The convention in literature is to make characters distinguishable for practical reasons, but in "real" history naming conventions are messy and people aren't always distinguishable. There are even real debates among historians about whether a name refers to multiple people or not!
Tom Bombadil is a similar thing. He serves no dramatic purpose. But a history, or a mythology, doesn't always have events that fit together in a neat way. Sometimes stuff just happens, or there are things that are only tangentially related. And it's difficult to draw a circle around events and say inside the circle is our story, and outside the circle not our story. There are other stories, intersecting.
He is the only character in the middle earth that can do that actually. The ring, and its immense power, has control over everyone else incl. Gandalf, Galadriel, and Sauron.
Just in case it wasn't a typo, you certainly meant 'entomologist'.