I have this route:
/ip route add dst-address=4.4.4.4 gateway=177.89.160.1 comment=FailOver
And i trying this and don’t work.
/ip route remove [find dst-address=4.2.2.2]

I have this route:
/ip route add dst-address=4.4.4.4 gateway=177.89.160.1 comment=FailOver
And i trying this and don’t work.
/ip route remove [find dst-address=4.2.2.2]

You know, that 4.4.4.4 is not the same as 4.2.2.2 - so there is no surprise
.
Still - use quotation marks, /ip route remove [find dst-address=“4.2.2.2”]. Or even better:
/ip route remove [/ip route find dst-address="4.2.2.2"];
yes dst-address should be in CIDR form
/ip route remove numbers=[find where dst-address="4.2.2.2/32"]