I haven't noticed this issue when I use the ESPN app, but it sounds like a bandwidth constraint issue (server or client). Since you can only control the client end of the connection somewhat, make sure the Roku has sufficient stable bandwidth (Settings/Network/About).
Try switching to the other wireless band (2.4Ghz or 5Ghz) or wired if your model supports it. Restart your Roku if need be as well. Also make sure you have the latest version of the ESPN app (3.2.2020092400) and RokuOS (9.4.0-4188).
Yes, happening to me too. It has nothing to do with my internet or bandwidth. Every other channel & app (including the ESPN app) work fine. It's only ESPN on Hulu. Anyone from Roku have any comment on this? It's really annoying. Also, these constant issues with NBA broadcasts is getting old. TNT had big issues only on Hulu last season!
Its most likely the ESPN feed itself - even with linear MVPDs (with re-compression) the quality is normally poor - with YT TV and watching MNF this season, the quality was abysmal at times, with bitrates often dropping down to 1-4Mbps (compared to 20-60Mbps for most content).
In contrast, today's Wildcard game - co-broadcast on ABC - was very clear with none of the "normal" visual degradation seen on ESPN/ESPN streams - at least OTA on ABC (I didnt watch it via YT TV or the ESPN app, because of the quality issues with ESPN/ESPN streams).