I think it can be misleading to think RRC are used to eliminate ISI. The only purpose of Raised Cosine (RC) and Root-Raised Cosine (RRC) filtering in the transmitter specifically is to constrain the transmission bandwidth when spectral efficiency and out of band emissions are concerns (as they are in most wireless communication solutions!). They achieve this purpose without introducing ISI in the process.
If we must reduce bandwidth, improper filtering can introduce ISI. A Raised Cosine filter is one solution that constrains the bandwidth as needed with zero ISI. By splitting the filter into two matches RC filters, we achieve the desired filtering of the spectrum at the transmitter and a matched filter in the receiver (which then optimizes SNR under white noise conditions).
If we have an equalizer in the receiver, we could theoretically use other filtering options to achieve the bandwidth reduction, knowing that we still want to have a matched filter in the receiver to optimize SNR. However the effective delay spread of the filtering will rss with the delay spread of the channel and therefore increase the required length and therefore complexity of the equalizer. Another way to say this is we are losing degrees of freedom in the equalizer by (needlessly) introducing ISI when an RRC solution can easily provide what we need. So, given we need a filter in the transmitter (and that need has nothing to do with ISI, we just don’t want to add ISI in the process if we can help it), and given we want a matched filter in the receiver, the RRC filter achieves both of these goals.