France is a state with better centralization than any European country. No matter how developed regional communes are, they absolutely can't replace Paris.
Politics, administration, transportation, economy, population too. France has one city controlling the country.
If such Paris falls, we need to reevaluate France as a force.
This isn't something I can change by doing something, nor an area Russian forces can block by fighting harder.
Perhaps those who knew that atmosphere best were the French and British ambassadors residing in Russia.
"Tsar! France will absolutely not abandon Paris!"
"If you move Commander-in-Chief Brusilov to pressure Berlin just a bit more, we can instantly push the front back to the border!"
"BEF organization really almost complete! 700,000, no, million-strong army by next year! War Minister Kitchener promised on his honor! Please believe us!"
Even to them, the Western Front was just brutally trampled.