I've seen an interview with a General who said he had done a lot of in-person analysis of their military and came away surprised at how mediocre it was, from equipment to leadership to planning.
Mariupol was practically taken in 4 weeks (plus a sweep from the remnants of the nazis for probably another 2-3 weeks) by a small group of troops (estimates were given of about 7-8 thousand) against the AFU of which there were "officially" 14.5 thousand people. The ratio is 1:2.
For comparison, Mosul was taken in 8 months (plus it was cleaned from Islamists for another 3-4 months) by a group of about 100 thousand people, against 9-10 thousand defending Islamists. The ratio is 1:10.
Aleppo, with a similar number as Mariupol (400-450 thousand people), was defended for 2 years, so a person writing about the weakness of the russian army is either a fool, or a russian spy, trying to show the strength of the russians as very weak.