I'm not sure I understand, he bested Haryanto and matched Ocon at Manor, and beat Ericsson in every single race at Sauber. I'm not sure what more he could have done. For me, he stands as a driver who was unlucky to land in F1 when there wasn't a clear space for him rather than a driver who was pushed out by better. I still think Mercedes should have given him the seat they lent Bottas instead.
Hayanto is hardly a good yardstick, someone who averaged 13th across his full-time GP2 career.
Ocon only raced from Spa so it's a bit difficult to compare him side-by-side to a driver who had been in the car all season.
I just mean compared to Ericsson Wehrlein looked a bit mediocre compared to how exciting Leclerc has looked. That might be down to other factors of course, but Wehrlein just didn't look great compared to what isn't classed as one of the up-and-coming driver, while Leclerc does.
Wehrlein out-qualified Ericsson 11 to 7 (average Q1 difference 0.050 seconds in favour of Wehrlein)
Leclerc has so far out-qualified Ericsson 11 to 3 (average Q1 difference 0.468 seconds in favour of Leclerc)
Of course there's more to it than that, as you posted racing stats for example, but to me it suggests that Wehrlein simply doesn't have the pace of Leclerc, while Mercedes will be hoping Ocon is challenging Leclerc in the future.
The way things are going this silly season Wehrlein could end up in a Toro Rosso and reignite his career, and hopefully he does; he's clearly got ability, but as of yet he hasn't stood out like a driver capable of potentially replacing Hamilton, which was the aim.