Gotta have the car or, with rare exception, you ain't winning it. And boy did Lewis ever have the car. IIRC 2023 was his only year in an F1 car that wasn't a race winner. Lewis is/was awesome, but if Michael doesn't decide to retire when he does - when Lewis desperately wanted out of Mclaren, was without a ride for the next year, and was looking for any good landing place - Lewis is very likely still a 1xWDC (which is great, don't get me wrong). He'd have been on the outside looking in with everyone else, while Nico very likely becomes a multiple WDC and maybe Michael pads his total on the way out if he could beat Nico, which is far from a given considering their respective form as teammates. A Merc driver was gonna win those WDCs either way, and who knows, maybe 2021, too.
I also still really think Lewis was ready to retire as a champion in 2021, and only stayed because that didn't happen. No proof of course. Just my gut. I doubt he'll ever be that sharp again. But who knows. I'd be happy for him to be that guy again. It'd be great for the show.