This is valid
I use NextDNS in combination with a VPN, but I do so because I like the control panel/logging and the flexibility, not just the content filtering.
IF content filtering is the only reason you are using NextDNS there may be a straightforward, robust, and elegant solution. Many VPNs have content filtering built in. I believe this includes all of the top VPNs from this sites VPN comparison. If you go with one of these VPNs (e.g. Mullvad, iVPN, Proton, AirVPN, Windscribe) you can kill two birds with one stone, and do so in a more robust way (content filtering and hiding your traffic from your ISP). This assumes that you use your VPN 100% of the time. One advantage of this is that dns queries and content filtering happens within the virtual private network.
Another possibility if you are technically inclined. Since you don’t care about ‘blending in with the crowd’ or fingerprinting/appearing unique, you could rent a cheap VPS (<$5 a month) install Adguard home or Pi-hole for DNS filtering, install Wireguard, Tailscale, or some other VPN software and you’ve got your own VPN with content filtering built in.