Starfleet alternates their shield and phaser frequencies, when fighting the Borg. This was stated on screen. There's no way that we could ever be equal to the Borg. It just doesn't work that way. It's like saying that one day, we're going to make germs go away. No, we're not. It just doesn't work that way.
The reason they kept finding loopholes is because the writers decided that they should find loopholes. Nothing more.
What is this, Deadpool?
The crew of Trek knows they're finding loop holes due to the writing staff?
Are we arguing Trek Universe facts or real world writer facts because I've lost track?
Well, whatta you know, I'm a writer, too. Small world/big Internet. They didn't have to sabotage anything. When creating an enemy that's outrageously overpowered, the best thing to do is (a) keep their appearances to a minimum and (b) all encounters with them must lead to HEAVY repercussions/casualties. Anything less than this is incompetence.
It happened with Doomsday. It happened with Venom. And it happened with the Borg.
As a producer, one of my main priorities is to my audience. They are what draws in sponsors to create revenue for my show. The Borg, like Venom and Doomsday proved to drawn in viewers/readers/money. TV is a business just like any other. So if my audience is telling me they really like the Borg, Venom & Doomsday by increased sales/viewership, then it's incompetence on my part for not filling the supply of that demand.
The Borg are fan favorites.
Every time they showed up, viewership increased.
Voyager was a show that needed to keep up it's ratings, so as a writer/producer you do what is best to keep the show on the air. If that means showing the Borg every season to get folks to watch, you do it. If the fans don't like it in hindsight, it's too late. While the show was on, feed back for the Borg was positive.