The good news …
No boxyness, negligible mains hum/buzz.
The bad news …
The level on seems low, (lower than your other recordings).
Amplifying low-level sound (in Audacity) also increases the hiss noise.
Noise-reduction reduces hiss, but can make the voice computery sounding.
Ideally minimize the hiss in the first place by experimenting with different gain control settings on the mic.
At some gain setting there will be a goldilocks-zone with the best signal-to-noise ratio.
The sibilance is too a bit too strong. To desibilize with Paul-L’s de-esser …
Step #1: measure the RMS of your audio, (the ACX check tool tells you that).
Step #2: Apply Paul-L’s de-esser with these settings: set the threshold to the RMS you measured, plus 1…
(If too much de-ess is applied it will sound like you’re lisping).
I don’t think it is possible to reduce sibilance other than by processing the audio.
The off-axis trick helps reduce mic-popping plosives, but not sibilance.