And without stealth, it isn’t the handful of J-20s that are the problem, it’s the 500+ J-10s (Their F-16 copy). It can outrun, outturn and outrange a 35 that has lost it’s stealth.
The 35 is designed to prevail in two environments, one where it is protected by F-15s and 22s, and another called the “defense procurement process”.
The F-35 is only sort of kind of stealthy head on - otherwise its huge. F-22 has the RCS of a small bird for comparison.