Why there’s no mention of the built-in optimizer in this topic? You’ve forgotten about getting concerns by said it’ll be enabled by default? You didn’t even (start) consider to make it be disabled by default at least in its initial release?
As others said - please put the built-in optimizer behind opt-in flag on initial release; otherwise you’ll face opposite effect. No matter you want to make it be enabled by default on some point (even near future). so users including me will not affected by bugs in that. You will not able to said “We’ve done w/ betas so it’s applying, you are free to opt-out it if there’s breakage”: Breakage is affect you negatively.
Since you’ve taken long time to fix single bug according to canny, users including me concern it’ll happen on the built-in optimizer.
Anatawa12 and dark, both are author of their optimizers, have said there are edge case on Unity’s asset. They gave a warning on you - don’t ignore that. I think it’s your responsibility to said “we’ve considered” before its release on live channel, at least.
p.s. In general, be able to only previewing before applying the built-in optimizer isn’t enough to check whether there are any breakage by it. This doesn’t change when apply optimization from AAO or d4rk one: please cover about how users can investigate mangled breakage in the document.