My critique with your analogies is the Niko has been in the CS scene longer than Valorant has been around. He is a 9x Top 20 player of the year. Valorant definitely needs to take a couple more years to really put players like Leo's legacy to the test of time. The league examples are somewhat fair but I would argue that the Zeka comparison is more akin to someone like Demon1 who won Champs but has never quite hit the same peak since. You could also throw in Zeek and Cned.
If you want to divulge into the pre-2023 history for Leo, he was on GUILD which had some promise, but was competing against the likes of FPX, FNC and TL. Even then, they couldn't get past teams like OG LDN UTD and NAVI pretty much because GUILD was not great outside of Leo and Sayf and a bit of Trexx. But Trexx was and still somewhat is kind of a middle-of-the-pack player who has a high ceiling. Koldamenta, Russ and Yacine were all not really great. Despite this, Leo was still putting up numbers on GUILD which is why he got the move to a winning team. Think of it like Lebron switching from the Cavs to the Miami Heat.
Time will definitely test Leo's legacy, but his retirement is undoubtedly impactful for the community and I don't think it's an overreaction when other players and his former coach still hold him in high regards.