I find this is usually due to one of the following reasons:
- The proposal is discussing a niche topic that many people are not interested in.
- The proposal is poorly-written and people are not willing to put in the time and energy needed to fully develop it.
I tend to find that the best way to get useful feedback on a timely manner is to share the proposal on one of OSM’s many chat communities, which tend to result in faster response times.
Unfortunately, persuasive writing is a fairly challenging skill to get right and there is no obvious feedback when you’re missing the mark beyond a lack of engagement and negative responses when the proposal goes up for a vote. If the topic is niche, then there is often not a need to go through a proposal at all - just document the usage under the principle of “any tags you like”.