Now that The Sims 4 is free to play, should Digital Deluxe Upgrade be free as well?

Deluxe upgrade is pretty irrelevant so it doesn't matter if they charge for it. Only a completionist or someone who doesn't check what’s in the packs would buy it since it's clearly the worst DLC. I got it free myself as they did in fact give it away for free at one point.

I also disagree with the claim of base game being just a shell. I played it for half a year with no DLC and was happy with it. It has also received significant upgrades since then. In my opinion you should not spend on DLC unless you enjoy the base game itself.