My partner's family have a beach house in Robe so we head down every couple of months. For us it's the perfect 'getting away from it all' destination. Not sure how it could be overrated - it's just a lovely little fishing village/holiday town. I emphasize the little!
We love Robe for the tranquility, beautiful beaches (great for swimming and we love Long Beach, which you can drive on), visiting the 5 or 6 wineries around Cape Jaffa and Mount Benson (a 15 min drive from Robe back towards Adelaide), taking a day trip to the wineries in Penola and the Coonawarra (an hour's drive from Robe), fish and chips at the beach, amazing seafood (Robe is a lobster fishing area). There are also beaches where you can snorkel, spear fish and surf. There are also enough shops to potter around in on the main street for a couple of hours - half a dozen nice gifty/jewellery shops selling cute things for your house, a few clothes shops, an art gallery and the most lovely bookshop/cafe I've ever been to.
I can understand that if you're just looking for a weekend away on the beach then you could well drive down to eg Rapid Bay, Second Valley, Normanville etc and save the much longer journey to Robe (takes us 3.5 hours from Glenelg plus stopping time for a wee/coffee/stretch the legs in Meningie)and we mainly go as we are lucky enough to have a house to use there.
I think Robe is a great stop on the way to the great ocean road/grampians etc - lovely spot to spend 2 or 3 nights and do not very much at all. Just dont' go expecting a big bustling town with loads on!