to completely block packets via routes with gateway 172.16.30.12 you may try something like
/interface bridge add name=blackhole protocol-mode=none
/ip ad ad ad=192.0.2.1/30 int=blackhole
/ip route add dst-address=172.16.30.12 gateway=192.0.2.2 scope=1
yep, kinda perversion…
but I don’t see any good solutions