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.

Artillery is only viable on Ukraine's side because Russia is too incompetent to manufacture long-range (30-50km) FPV strike drones at scale. Currently only Ukraine has pushed the "kill zone" to the 15-25km mark. Russia is behind. But this situation will not last, drone technology will improve on all sides, China will innovate on drone range and Russia will buy those drones. The drone "kill zone" will surpass the range of artillery for all sides.

This is happening in a few years.