

The isolation Russia is a direct response to the 2022 invasion. Before that, Russia was a member of the G8, a massive / main energy partner to Europe, and widely integrated into the global economy. Those bonds where cut after the invasion, not before.
Regarding you second question: I don’t see many other options for the Ukrainian government. The tragedy of forced mobilization on both sides is clear, but the responsibility for that tragedy is by the party that made mobilization necessary in the first place.

Equating the Donbas conflict to Gaza ignores the presence of Russian regular forces and proxies documented since 2014 or so. Ukraine was defending its borders against an insurgency backed by a foreign power. In this localized conflict both sides broke ceasefires multiple times.
Why is the encroachment story a reason for invasion? This move actually pushed Finnland in to Nato. If the invasion should have been a move against Nato it wasn’t a smart one