When asking "what's the default gateway?", more often than not, the real question you have is "what's the gateway to IP address X", which would be:
ip route get X ip route get XI do use ip route a fair bit - if I have a machine connected to two (or more) network segments and want to ensure traffic gets routed back the way it came
However my main criticism for "ip route" is that it's inconsistent and a change route "route"
"route" does reverse dns lookups - e.g "my.server.tld rather than "1.2.3.4", or "default" rather than "0.0.0.0"
"route -n" shows 1.2.3.4
"ip route" doesn't do reverse lookup, however it does say "default" rather than "0.0.0.0".