Yes, the eRT is "only" an ODA application which has existed for a long time. However, for practical operation of this function, you encounter the limit of the transmission capacity of the original RDS. For this reason, the latest edition of the RDS standard does not even consider the option of transmitting eRT within stream 0. This is logical, because the transmission capacity is just right even with classic RT and since eRT is not backward compatible, both must be transmitted.
Without full support for RDS2 on the receiver side and without explicit acceptance of this system by the authorities carrying out technical supervision, we will probably not be able to move forward. Although radio stations were expected to be the driving force behind this development, the opposite is true. To this day, most stations are unable and unwilling to broadcast even RT+, which is a 20-year-old feature... There is almost zero interest in the eRT from the stations. The fact that eRT can sometimes transmit slightly longer text is probably irrelevant. The radio industry is more focused on keeping messages as short as possible, while providing more information via hybrid radio services. The eRT+ is still limited to 64 characters - no progress here. I see the real benefit of the eRT in Unicode support, which is unfortunately proving to be a marginal topic for the part of the world where FM broadcasting is widespread. There could be some benefit in countries where an alphabet other than the Latin is used.