The “legacy” way you described was the way of doing it on devce without switch chip or if switch chip did not suport VLANs. The legacy way of doing it on devices with decent switch chips was to use /interface ethernet switch part of configuration and using single bridge … the high-level config was the same as the “new”, bridge vlan-filtering, way. Beware that even if your device does have switch chip, a few things might or might not work, such as hybrid ports (one or more tagged VLAN and one untagged that should be tagged in ingress and untagged on egress). Mixing tagged and untagged traffic on bridge can have some side effects as well.
This (switch-chip based VLAN setup) is still viable way of configuring it in ROS versions 6.42+.
There are a few topics on this forum with discussion about old and new ways, including this.