I'll give 5 stars to Nuclear Throne because I have a deep fondness for this game, and it brings back a nostalgic feeling from when I used to play it in the past. Besides that, I really enjoy playing it.

That being said, I believe the game can truly be rated as 5 stars for some or 3 stars or even something in between those numbers. Nuclear Throne shares a similar issue with Hades, in that it creates a barrier that divides most players into two types: those who only see about 20% to 40% of the game and those who experience approximately 100%.
In the case of Nuclear Throne, this barrier is the fact that the game relentlessly challenges you in so many ways that it sifts out those who play it, and it can be very discouraging for many players because everything kills you, everything deals abnormal damage, some weapons you can use can kill you, and what drives your progress is sheer persistence and the desire to win.
This might be interesting, but only for those who truly enjoy this type of gameplay, as you will die many times and become frustrated until you finish the game. This problem prevents many people from even getting to know all the enemies, seeing all the weapons, defeating all the bosses, collecting all the collectibles, and unlocking additional game modes beyond the initial ones.
Setting aside this issue, the game, for those who enjoy this kind of gameplay, is quite enjoyable and interesting. Runs are fast (since you die quickly, and it generally doesn't take long to reach the final boss compared to other games of the same style), you become attached to the characters (with a total of 12 unlockable characters plus two secret ones), and for hardcore players, there's the possibility of collecting 12 crowns for each character, which adds more challenge and gameplay hours.
Overall, I like how the game is fast-paced, dynamic, with characters I've grown attached to, a nice visual style, good music, and sound effects. It appeals to the type of games I enjoy playing, but I completely understand the criticism of those who find the game mediocre or worse.