I have a Pixel also, and have issues with is since the change to Gemini. It works _most_ of the time, but every once in a while it'll tell me it can't set a reminder.
I use reminders often so I suppose it is a low failure rate.
But, when they first made the change to Gemini I had to switch back for a few weeks/months before it could set reminders properly.
I've set a reminder through Gemini, then tried to change its time. Told me there are no active reminders to change. Created another reminder with correct time. Got both reminders.
I said "Hey Google instead of reminding me about the bananas on Tuesday, remind me on Wednesday" and that worked. It's quite possible these things only work on Android 15 QPR 1, or only on a Pixel Pro, or who knows. Its capabilities have noticeably expanded in the last few months. One thing I know it still can't do, that the old Assistant did, is control a Sonos.
ETA: The joke is I don't even have Google Tasks installed, so I am not sure what effect those Tasks items would have. They might only surface on the side pane of Gmail.
I want the reminder not on my device, but on my work computer which I'll be staring at when I need the reminder. Or in the bananas case I want bananas sent to our shared family grocery app (which isn't a google service) so that if my wife happens to be going by a store tomorrow she knows to stop and get some along with flour or whatever else we need to stock up on.
I use reminders often so I suppose it is a low failure rate.
But, when they first made the change to Gemini I had to switch back for a few weeks/months before it could set reminders properly.