I disagree even in that case. When my colleague complains that a certain software module is overly complex, say, that’s really useful feedback even if they don’t have time to itemize the specific reasons why or propose alternatives. In terms of delegating and scheduling, it might just fall on someone else to take the complaint and look into whether the code can be simplified.
Raising a complaint long before having a full alternative is really useful in matters of team conventions, design principles, adoption of different tooling, workflow policies, etc.
I would always want to foster an environment where teammates could feel free and empowered to speak up about a topic that doesn’t sit right with them, and never feel implicit pressure to be quiet or keep to themselves if they cannot already propose an alternative.
I like to say that it’s all about empathy, but people often think about empathy completely backwards, from their own point of view, just “not wanting to hear it” or getting annoyed with a particular colleague who is often vocal just because they irrationally wish the person would be quiet and not introduce extra work via some complaint that needs looking into.
This is backwards because you should be happy and welcoming for people to tell you all this stuff. Part of being a professional is increasing your capacity to absorb complaints to make other people happy by solving their problem when they alert you to it, and not getting upset or annoyed (or at least not letting it affect you), and thinking they should be holding back for your sake.
It’s a natural extension of a lot of the advice in, “How to win friends and influence people,” applied to the workplace.