Hi,
Microsoft has reduced their bandwidth and quality settings to 720p or less in some cases with the surge of usage due to the covid-19 pandemic which has led to a high peak of Microsoft Teams usage worldwide. Until they upgrade to meet demand or people go back to normal life we won't be able to really get solid video through the service for some while.
Reference:
https://techcommunity.microsoft.com/t5/microsoft-teams/poor-videos-during-teams/m-p/1290304
(If the reply was helpful please don't forget to accept as answer, thank you)
Best regards,
Leon