The Spiral Abyss is probably the only end-game content in Genshin Impact at the moment. The Abyss enemiy lineup keeps changing with each new update which requires players to have flexible team compositions.
Each Spiral Abyss floor grants a different stat bonus which is often tied to a certain element. This requires players to have a diverse set of Genshin Impact characters that can benefit from that bonus which has a great impact on their results in the Abyss. However, there are a couple of characters that can be used for multiple floors which makes them irreplaceable for most parties.
An interesting post on the official Genshin Impact subreddit has revealed the most picked Spiral Abyss characters for the current update 2.5. The chart is taken from the popular stat website named GenshinLab. This chart represents the pick rates within the playable roster for each account, meaning that 91.7% of players that have Zhongli have actually used him in the Abyss. He is probably still the most picked character overall since, unlike Kazuha, a large portion of the community has pulled for the Geo Archon, especially since he had a banner re-run in Genshin Impact update 2.4.
Since Hoyoverse introduced Geo buffs to the game, Zhongli has become one of the most popular Genshin Impact characters. He has the ability to lower an opponent's defensive stats, which is especially important in end-game content. He is probably one of the most flexible characters alongside Raiden Shogun since he fits in with almost any team composition.
Similar to Zhongli, Kazuha was not well received in the Genshin Impact community at first, but he turned out to be one of the strongest support characters in the game. He was usually perceived as a slightly weaker version of Venti because they share the same element and have a similar Elemental burst. Luckily, multiple Genshin Impact leaks have revealed that Kazuha might get a banner re-run in the foreseeable future.
Bennett is still one of, if not the strongest four-star Genshin Impact character, thanks to his stacked and adaptable kit. He is still the go-to support for most team compositions that need a strong healer. His build should revolve around buffing allies for extra damage. Another one of his strengths is that he can create a lot of energy and elemental particles which allow players to refill their elemental burst faster. His Elemental Skill (Passion Overload) can create a decent amount of particles, and it has a low cooldown.
Genshin Impact is available now for mobile, PC, PS4, and PS5, with a Switch version also in development.