ERA is useless against latest APFSDS rounds, nothing saves you from the kinetic energy of 30kg of tungsten.T90M is far superior to VT-4 in almost every metric, mobility and some electronics will be the only exception.
T90MS is the export variant of this tank. It is also superior to VT-4 in the same metrics. These are only operated by Russia.
T90AM is the previous modernization of T90, its export version is T90SM. That is the one india was considering, but will never get, they ordered more old T90S instead.
The SM (not the AM) has Relikt ERA and an APS and if equipped with the Svinets series of ammunition, it beats the VT4 in protection and firepower any day of the week. But VT-4 has better technology and mobility than this variant.
It is unfair to compare Oplot-M to T90M. Oplot is nowhere near as good, not even as good as VT-4. 90M on the other hand is even better than T-14 in some regards.
Latest ATGMs too can be made simply large enough to defeat any armour, or use top attack, or be launched in quantities to defeat armour in repetitive hits
Not being hit in the first place is a key.
And if you don't have sensors to detect the direction of attack, it means you loose at least 3-4 tanks if the first tank hit can't relay the info where it was shot from.
Even if the tank will survive a hit heavily damaged, it means nothing if it can't fire back.
It will likely be immobilised, with crew incapacitated, and be finished by the next hit.