As someone who flies rotary and FW, with TCAS in the FW, I can attest that it’s not a good solution on its own. Often the warnings come very late, and a decent lookout is the best first line of defence.
I do think there are bigger issues which should be fixed before mandatory TCAS though. Such as the glider pilots from Bicester who sit at the end of Oxford’s Instrument approach watching G5s almost hit them, saying “I can’t have a transponder because they take up too much battery power”...