I think Apex is the closest any FPS game came to replicating the potential that CSGO had. It was the only game that not only had the movement, feel-good gunplay, and money pumped into it, but it also was super enjoyable to watch from player POVs. Overwatch struggled immensely with the visual clutter and how time-to-kill was extremely long for pretty much every character because of the presence of healers and tanks. Apex unfortunately never was going to rival CSGO because it's a battle royale game, so competitions naturally were not team vs team, but team vs team vs team vs team vs team vs team and so on. Still a very enjoyable game with high skill ceiling.
VALORANT is now the only FPS that rivals CSGO because... it's a copycat. Very similar guns and formatting. Former CS pros were instantly dominant when the game was first released, and still have a leg up on naturally adopting the game. Only real difference is the introduction of class-based abilities. Tanks the watchability of the game, but zoomers like the bright colors. Oh, and tons of money was pumped into it by Riot.
The only eSport that still not only rivals but probably surpasses CS is League of Legends. It's a team based game that is fairly easy to watch IF you are familiar with the game (and if not, then yeah its pretty hard). It gets a massive amount of money and time spent by Riot, the game is balanced, lots of individual skill can change the game, etc. But its not an FPS and it's most popular in Asia, so we don't really talk about it on tftv that much.