Ground movement radar is excellent where it can see - you can tell the difference between an A320 and B737, such is their resolution
The "new thing" is to have a Mode S based system with lots of receivers that triangulate positions, but that also has blind spots and unreliabilities, but it is also a calculated rather than measured position that appears on screen. That is what DUB uses and I have been victim to their system's shortcomings a few years ago. I do not believe it to be a very accurate system.
Not so "new" now, and in widespread and successful use at many airports much busier than DUB.
But you are correct in that multilateration (which uses TDOA, not triangulation) has limitations compared to SMR - it doesn't tell you anything about the size or orientation of the target and in fact it will only accurately fix one point on the aircraft (the transponder antenna) and so normally only forms part of a hybrid A-SMGCS system.