The star ratings for this game are irrelevant. Into the Breach is such a weird animal, that you can barely rate it as a video game. It is more akin to a solo board game. I call it that because you can easily finish it in one sitting (1-2 hours), depending on the difficulty level, as well as on how many islands you decide to liberate before launching your final assault upon the enemy.
If you're looking for a story, or a long winded-campaign, then try somewhere else. Into the Breach will only appeal to you if you enjoy pure experimentation, or if you are a sucker for high scores and rare challenges. You could also easily play it to pass the time. In fact the puzzly goodness of every combat scenario surpasses any Sokoban, 2048, or Sudoku experience.
Another reason to avoid it is if you want to experience fierce mech-vs-kaiju combat. The game is actually packed with that, but only if you imagine it. The graphics feel nice and warm, and the Vek monsters as well as our mechs look like cute plush models, However, units move like pieces on a board and animations are limited to idle wiggling and impacts of various kinds (also very cute).
My personal appreciation for this game comes from the immense variability that comes with unlocking mechs and pilots. It allows me create custom challenges, or just enjoy a random selection of metal warriors. It's not addictive, but it can become a favourite past time if you have ever enjoyed physical games like Vlaada Chvátil's Mage Knight, or any cooperative tabletop title that you can play solo.
It's REALLY GOOD!