There are good candidates, but they could not beat Biden in 2020 and it is very abnormal for someone to run against an incumbent President of their party. As soon as Biden was running, the game was over.
Buttigieg, Harris, Whitmer, Newsom, Moore, Booker, Shapiro, Allred are all qualified and may run in 2028.
I like Klobuchar a lot and thought she ran a good campaign in 2020. I also like Chris Murphy, but I think he wants to be Governor of CT first.
The key is to pick someone similar to Biden's moderate bipartisanship positions to hold the center and reach out to both wings on certain policies. That is why Biden won in 2020 - sure the danger of Trump was there, but voters knew Biden was not a radical nor a reactionary. They would be in good hands with him until the storm blew over.