For context, I work on a software development team and I have a teammate we'll call Bob. Bob regularly comes up with ideas on how we can improve things and proposes these ideas to his teammates. In general this is great; there is always room for improvement in processes, architecture, design, etc.
The vast majority of Bob's ideas however are not good ideas. He will come up with Idea A, and within 10 seconds or so of hearing it the teammate to which he's talking can think up reasons X, Y, and Z as to why Idea A is not feasible. That teammate will calmly and rationally explain reasons X, Y, and Z for not taking up Idea A and Bob will not accept those reasons. What always proceeds is a 10-60 minute drawn-out conversation/argument eventually leading to Bob letting the topic go and nothing having been improved.
After a few years now of this happening on at least a weekly basis, I'm tired of and frustrated with it. I'd like to let Bob at least feel heard because I don't at all want to discourage ideas for improvement, but I don't want to keep wasting time over things that at face value can be immediately dismissed.
How can I better nip these ideas in the bud when they come up? Or how should I proceed with this type of scenario?