Last time (like 2 years ago, haven't played much since) I checked it wasn't exactly 25 MMR per match. It does depend which team has higher overall MMR to begin with, and values adjust from that 25 value.

I had an MMR of around 4.4k solo/team, I think the average player had 2.25k MMR, the standard above average player had around 3.5k to 4k MMR. Anything past 4k MMR exponentially made matches way more intense. Its always been this way as far as I remember even back in DoTA 1 days

4k MMR in DoTA skillwise is about the equivalent of Platinum in rocket league, or Diamond in Overwatch