Holding a lessons learned meeting after the conclusion of a proposal is a good idea. But only if it results in change, and ideally a set of action items. It's not a place to vent. It's a place to turn experience into inspiration.
Some lessons learned can be addressed by changing the process. Others can be addressed by providing training. Ideally, any training required can be incorporated into the process, instead of being treated as a one-time event.
With each issue that you face, if there is an improvement you can make to mitigate or improve it in the future, make the change in the process. Then the next time you execute the process, you can take advantage of the lessons learned.
When holding a lessons learned meeting, you can also use this approach to keep the discussions productive. When an issue is raised, you can ask the attendees, “What changes could we make in the book to circumvent this issue in the future?” You want your lessons learned meeting to be more about improving your future win rate than about what went wrong.
Any resource issues should be addressed as a return on investment issue instead of a cost issue. What would the investment have cost and what would its return be? Moving forward, how should the company invest scarce resources with regards to proposals? How does that relate to win rate and the return on investment? The more you can do to quantify resources issues and win rate impacts, the more you can minimize opinions and focus on making, more informed decisions in the future.
When considering proposals, you should have a holistic view of what contributes to the win rate. For example, you might conclude that because assignments were submitted late, you need better enforcement of deadlines. But if the problem was that the authors didn't have the information they needed about the customer, opportunity, or competitive environment, they might have had more difficulty completing their assignments than they should have. The same can be said about reviews. If there were defects at a review, was that because of presentation defects or inadequate information about bid strategies, customer preferences, differentiators, etc.? An effective lessons learned review needs to dig deep to find root causes in order to actually achieve the desired changes.