NXT has 250 assets and is adding 2 assets/day = it's going exponential...
You haven't seen Dogeparty adding assets, now THAT IS exponential!

They added a few thousands assets in two weeks, because it only costs a few cents to issue an asset. It costs ~$30 to issue an asset on NXT at current exchange rate, so 2 assets/day is not that much and not exponential at all.