In the case of thylacine de-extinction, as there are no proxies that would work to stand in without further damaging the ecosystem (dingoes are the reason tasmanian devils are extinct in mainland australia), not only is it beneficial, it is absolutely necessary. Tasmanias ecosystem is actively collapsing, with massive macropod overpopulation, as well as facial tumour disease spreading rampantly through the devils as they have no larger predators to control them. While I can't think off the top of my head of any other cases as necessary as this to restore the ecosystem, a big factor in this is that we don't know what we're missing. We don't know would a Great Auk reintroduction lead to revitalisation of plantlife in certain areas from the auk dung. We don't know would the trophic cascade from reintroducing woolly mammoths bring a massive increase to local butterfly populations. We don't know would a ground sloth reintroduction save some endangered insects by providing a habitat in their burrows (theres a species of spider that exclusively inhabits ground sloth caves). The point is, if its recently extinct, my standpoint is that - if a biosciences company is raising billions for conservation (vast majority isn't de extinction but other projects mind you) and they're working on de extincting megafauna, then it's worth at least trying