My experience playing Go Nuts for Donuts comes from both party settings (3-6 players) and competitive settings (2 players). I have played all variations both in person and on BGA. I have gotten Top 3 all time ranking in BGA Go Nuts for Donuts but mostly playing 2 player, though I generally find the 3-5 player variations more fun and enjoyable.
Here are my thoughts:
3-6 player Donuts is great for a relatively quick, fun, and casual game.
For the large majority of casual players, the most enjoyable form of Donuts is what I call "party mode" or 3-6 players. Having more players (especially for the 5-6 player modes) adds a significant amount of variability to the game as it is near impossible to predict what other players will do. Most of this game comes down to chance or luck, but it is quite fun and exciting when you manage to pull off a victory. Given the high variability, even inexperienced players have a shot at winning.
2 player Donuts is best viewed as a competitive, strategic, and some cases psychological game.
At the high levels, 2 player Donuts is a very different game than 3-6 player Donuts. Since there is only one opponent, you can fairly judge what your opponent is likely to want to play and what Donuts they want to pick. At the high levels, this is a game where it comes down to out strategizing your opponent and taking calculated risks when it favors you.
Some have complained that you would always just pick the best card. However, it is not always clear what is the best, and as the game progresses, what is best will change depending on the cards remaining in the deck and the situation you and your opponent are in. Part of the skill of the game in 2 player Donuts is to get an edge over your opponent and defend it and/or take a calculated risk (e.g. taking a chocolate donut or or early maple) to potentially gain an advantage. You need to out think your opponent and have a good understanding of probability (what cards remain in the deck and are likely to appear) in order to have success in 2 player Donuts.
Overall, in the context of a competitive game format like BGA Arena, I think 2 player Donuts is the best version of the game for a competitive setting. Two player Donuts is a competitive game, one very different from 3-6 player Donuts. That is okay. For those that like the "party game" style of 3-6 player Donuts, I would encourage you to continue playing those games outside of Arena.
It doesn't seem to make sense to get frustrated that a single season of Go Nuts for Donuts Arena is 2 player. Given that ever single prior season of Donuts Arena before this was 3-6 player, please let those that enjoy 2 player Donuts (even if they are in the minority) enjoy this season.
Thank you.