TBH it's probably for the best? Wonderman always felt like a project greenlit during the post-Endgame gold rush period. I didn't watch Wonderman, but if its' streaming numbers didn't seem to push the needle, I'd rather them consolidate their output way down from the last few Phases.
Besides Wandavision, MCU shows have basically done nothing but devalue the brand and cause fatigue in potential fans. They clearly want to reboot the MCU soon. The right move right now seems to be to rein in the output to maybe two films a year max, and the relatively rare TV show about 150% proven characters.
I just don't think there is enough energy to retain a notable Wonderman presence in the post-Secret Wars MCU, so, it feels like the right call to end it and move on to something new and bigger and better.