To be honest, its really not that many. The situation could be greatly improved without removal with: better organizing map categories like I tried to do ("Default" category problem), and folding 2,4,6, and 8 player versions of skirmish maps into one map. I think the redundant maps could be removed entirely, and maybe some of the niche maps like snowflake sea rocks could be a good fit for community maps.
Maybe I misread but are you advocating for removal without advocating for it ? I'm confused.
It's not that many yes. But if you consider ten maps per alpha updated with an alpha every year that's still about 25 years of upgrade.
My point isn't to burn all maps and start again. It's just let's consider the fun and most played maps and make them the prettiest we can and keep the rest in the community mod for people who need more.
Hiding maps behind options is as good as putting them in a mod IMHO. It also makes the download smaller which reduces costs with the bandwith and our finite server space.
Also most scenarios are broken and not really playable. A three map campaign by @Vantha would be a much better advertisement than 70 maps
Another problem we have is that most people making videos always pick the worst looking ones which is terrible for the game's image >< (Ducks behind the alpha label)