Is ip4 Still Relevant in Today's Networking Landscape? or What Are the Biggest Limitations of ip4 in

ip4 is relevant because it works. Simple as that.

ip6 has advantages, but until every device and service supports it fully, ip4 isn’t going away.

If you’re worried about address space, look into carrier-grade NAT. It’s not perfect, but it keeps ip4 alive for now.