Though, trashing your Duchy with Ritual gives you an extra point at the cost of a buy, so there is that.
Not just a buy, but $4 and a buy. So it's like a more expensive Great Hall in that case. Same situation occurs when trashing a Province. If you can trash the Curse, then the net effect of Ritual + trashing the Curse is roughly similar to buying an Island and setting aside the Duchy/Province (+2 VP and thin your deck 1 card, in 2 steps). However, Island is better in terms of VP for setting aside Estates, as Ritual+trasher only gives +1 VP.
Trashing a Gold basically costs you $7 and a buy for 5 VP (plus the Gold is trashed). You need some reason to avoid buying Province for this to be worth it, unless you hit exactly $7 this way and don't care about losing the Gold. An engine with Gold gaining could use this to extend the VP supply, if there is no other better source of alt-VP. This is probably the most common good case for Ritual, but it's still not that strong.
If you have useless actions late in the game, Ritualing one of them (such as Moneylender) could be better and cheaper than buying a Duchy.
I rated it quite low, and as the worst Event in Empires, but maybe it does better when you're playing all random. Empires has so much alt-VP available that something on the power level of Great Hall or Island is just not meaningful most of the time. On average though, I still think this will be about as impactful as Great Hall and Island, except without gainers working on it and with the added requirement of having a card you want to trash in your hand. Mostly I'm surprised that it's been rated higher than Island, which is fairly similar but easier to gain and use.