I think entering the battlefield tapped is a huge drawback and that drawback is magnified the more lands you play that ETBT. There is a limit on how many lands like that I'd play in a deck, especially an aggro deck. Adding 10 of them at once is not beneficial IMO.
I think the CLEAR #4 best lands that are also manlands are Colonnade, Tar Pit, Ravine and Vent. I'd play Inspiring Vantage and Battlefield Forge for sure over spires, and likely also Rugged Prairie - coming into play tapped is just terrible for this guild. In reality I also pick Clifftop Retreat above it in aggro (= almost always).
Sources that enter the battlefield untapped are actually critical in my experience in green because of mana elves so I'd play Llanowar Wastes and Blooming Marsh over Quagmire. Same with Simic.
In Izzet I can see playing Fumarole at #4, but the land is not amazing, just solid, and I think it is on par with Spirebluff Canal and Shivan Reef.
I think you are vastly underestimating how good 4 damage on post-wrath boards is for Boros. Plus, with the incredibly high density of good aggro 1's and 2's now, it's really easy to find a spot to drop a tapped land while curving out. Yeah, it sucks when you have a Plains Needle Spires hand and only R 1's, but I think the number of games you lose to that is way lower than the number of games you win due to having a wrath and sorcery-speed-immune threat.
I think it is best to break the cycle. 10 manlands are not necessary and they are not the #4 best lands in most guilds.
Huh? I do wonder, apart from Horizon Canopy, what lands you think are better than the manlands. I think that tarpit, collonade, shambling vent, raging ravine, fumarole, and needle spires are CLEARLY the #4 lands in their guild, and while quagmire and lumbering falls are meh, the other land options in those guilds are also meh as they don't super care about having access to a 4th untapped dual. The only one I could see replacing is reaches, and that's if the vast majority of rakdos decks in your cube are super aggro and it needs the blackcleave cliffs. In our cube we see enough mardu and grixis control that I think the summit is still better.
Edit - I guess if you were running the slow fetches and wanted a 3rd set of fetchable duals, but then you're so deep into lands I can't imagine not having the manlands anyway.
I think you are vastly underestimating how good 4 damage on post-wrath boards is for Boros. Plus, with the incredibly high density of good aggro 1's and 2's now, it's really easy to find a spot to drop a tapped land while curving out. Yeah, it sucks when you have a Plains Needle Spires hand and only R 1's, but I think the number of games you lose to that is way lower than the number of games you win due to having a wrath and sorcery-speed-immune threat.
375 unpowered cube - https://cubecobra.com/cube/list/601ac624832cdf1039947588
Huh? I do wonder, apart from Horizon Canopy, what lands you think are better than the manlands. I think that tarpit, collonade, shambling vent, raging ravine, fumarole, and needle spires are CLEARLY the #4 lands in their guild, and while quagmire and lumbering falls are meh, the other land options in those guilds are also meh as they don't super care about having access to a 4th untapped dual. The only one I could see replacing is reaches, and that's if the vast majority of rakdos decks in your cube are super aggro and it needs the blackcleave cliffs. In our cube we see enough mardu and grixis control that I think the summit is still better.
Edit - I guess if you were running the slow fetches and wanted a 3rd set of fetchable duals, but then you're so deep into lands I can't imagine not having the manlands anyway.
375 unpowered cube - https://cubecobra.com/cube/list/601ac624832cdf1039947588