They don't have many CaESAR'S themselves.. France had some 70 Caesars.. They have given/pledged around 18 or more than 25 percent of their stocks..
Germany has around 100 pzh 2000, and have given 7..
US has about 1000 M-777s.. and have given around 120..
NATO doctrine is built around US Airforce, which would be more dominant than Russian Air force in war, but, the airspace would be generally contested in a NATO russia war.. So, NATO has lesser artillery, as USAF would pick more of the slack of counter battery and fixed position destruction.. Russia has an abundance of artillery, because, USAF would be more dominant, and more Russian equipment would be destroyed by USAF than the other way round..
By stripping themselves naked of limited artillery stocks, NATO is upsetting the balance, as NATO/US Airforce can't be everywhere all the time.. as these stocks take several years to rebuild..