Why not a time bomb was because there was a serious risk of the Kazon disarming it.
Not to mention Tuvok needed several hours to activate the mechanism to send Voyager home, during which the Kazon had multiple more ships on the way meaning Voyager would have been overwhelmed long before they could send themselves home. It's why I always got annoyed at the maquis blaming Janeway for stranding them, she had no choice. It was either flee and let the Kazon have the array, or destroy the array and flee. Either way, Voyager wasn't getting home. If Voyager had tried to stay and use the array then the Kazon would absolutely have boarded and captured Voyager and either killed or enslaved both the Starfleet and Maquis crews.
I had to give it a rewatch, on second thought I don't think I actually ever had rewatched it after its original air date. Anyway, your take doesn't add up. The threat of the Kazon Ooga Booga getting reinforcements doesn't come up until after Tuvok and Janeway decide not to use the array, and during that whole conversation they aren't keeping up with Voyager's tactical situation. And Tuvok clearly thinks that they can in fact use the array. There's absolutely nothing to indicate that they can't hold out that long. The only concern they had while debating the issue was that once they left, the Boogas would get the array.
And the Kazon obviously wouldn't have just captured and enslaved them, because they made zero attempt to do so after the array was destroyed, even though Voyager had water-making capabilities which were apparently the holy grail for them. Voyager didn't run away at the end of the episode. The ooga booga did.
It was really sloppy storytelling.
A couple of other things that jumped out me while watching it...
Wow did Paris go in hard with his "Hey you Indian can't you turn into a fucking bird or some shit?". Seemed way more racist than I'd expect from 1995 Star Trek.
Neelix rescuing Kes was crazy too. That gremlin pretty much bamboozled Janeway and turned a first contact into a complete shitshow. Along with basically telling the Kazon, "hey you want infinite water, capture their ship!" Not only does Janeway not say shit about it, she just says fuck it and completely goes along with his play. No "what are you doing Neelix?!?", she just proceeds to keep treating him like a crew member for the entirety of the episode. And for good measure he zaps the water containers as a final fuck you. What? Ok, I can see the vague intent of that bit was for the Kazon to have to scramble to save as much water as possible thus allowing for their escape but... they had their phasers and the Kazon had dropped their weapons so..... just beam out?
Last thought... this really should have been the Tom Riker show. A little exposition to get the casuals on board with exactly who Tom is, Tom(renamed of course) Paris and Janeway penal colony conversation is an easy and natural place, or maybe the show starts with his Cardassian jailbreak. They could have used a DS9 for the jailbreak part where Kira makes good on her promise and gets him out and Voyager just starts with Tom back up to his old Maquis tricks. Anyway it's not hard to fit him in there. And the regular acting work would've saved us from Fat Riker in Nemesis where he fights some Reman in a comically lethargic action scene. Incidentally I haven't seen Nemesis since premier day in the theater, and that was the part that stuck most in my memory in a movie that was pretty bad across the board. Frakes didn't put in the treadmill time.
