Every MN coin has the issue that ROI falls as people buy more MNs.  However, this still increases value because as more people buy MNs, the circulating supply goes down, so the price of the 1000 POLIS collateral goes up.  You can't only focus on the ROI.  Look at DASH - the value is not just in the ROI from MN rewards, it's also in the inherent appreciation of the collateral.

Every new MN launch (and every crypto) is risky, so please only invest money you can afford to lose.  But to say "more MNs will reduce ROI" as if it's a bad thing is to attack every single MN coin, not just this one.  If you don't like MN coins, that's okay, there are plenty of other opportunities in crypto for you with different coin styles

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