Is DDR5 worth buying a new motherboard for?

No. If you already have a working DDR4 board, adding another 16GB stick or swapping to a 2x16GB kit costs ~$40-50 for the same 32GB capacity. DDR5’s speed advantage is small—maybe 5-10% in most games—while a new motherboard plus 32GB of DDR5 costs $200+ for a marginal upgrade. Unless you’re doing heavy video editing, 3D rendering, or data crunching that actually benefits from DDR5 bandwidth, you’re paying a lot for a little.