Eurail vs. budget flights for 3 weeks in Western Europe: What's truly more cost-effective NOW?

I'm planning a 3-week backpacking trip across France, Italy, and Spain this summer and am completely stuck deciding between a Eurail Pass and simply booking individual budget flights/buses. Every comparison I find online seems outdated, and I'm worried about hidden costs or time inefficiencies. I need current insights from someone who's done this recently – what worked best for you?