What does "with all its quirks and excesses" mean?

Well, quite simply, the Soviet regime was considered by many to be a quirky and excessively repressive regime. What's not to undertsand?

I got it~ Thx.

A lot of the bureaucracy associated with the Soviet Union could be described as 'quirky,' and the excesses are to be found in all dictatorial regimes.

Quirks are unusual policies or procedures. If an actor had to have grapefruit juice chilled to 5C every morning, that is a quirk. Quirks are unusual but not necessarily bad.

Excesses are things taken to extremes and is generally considered bad. If every official was rewarded with a car and chauffer, that would be an excess.