Ukraine is still investing in artillery plants, and it's why several other NATO countries are building more capacity as we speak (for their own and Ukraine's use). Artillery isn't any more obsolete than bullets, it's just not sexy, and at the margins isn't as strategically important.

You can't win a war without controlling ground. It's why the US lost the Iran War, and Vietnam before it, despite having an unfettered ability to pummel forces from the air. To control ground, artillery is essential. Not sufficient, but absolutely necessary.