Why losing so much mmr?

Can someone help me understand why I’m losing so much mmr for losses against stronger players? For example: I have cca 4900 mmr and I’ve just lost twice against players who both have more than 5000 mmr, one 56% winrate, the other 51%. For both matches I lost -60 mmr. When I a beat a player who has more mmr than me I gain max 20-30 mmr and when I beat a player who has less than me I gain just about 20 mmr. But I never get +60 mmr for any match. Is this system broken?

Yes. I have thought about this same thing many times and find it very frustrating. Makes progression impossible at times.