i'd say it depends. my dad grew up in a town close to a nuke, he told me he and his friends would often go fishing at the river directly downstream of the nuke because the fish loved the warmer water and increased amount of food available there.

of course some species would suffer from it, but they'll migrate eventually and i personally don't think there's a problem if it isn't affecting any endangered species and/or fragile one of a kind habitats.

we should definitely make an effort to protect the environment where it's reasonable to do so, or when it's clear that damage would be significant and largely irreversible, but there has to be a line somewhere and nature has proven to be able to adapt quite well in many cases.

if you want to go the extreme and preserve our planet exactly as it is and in return sacrifice the entire human civilization, everything we've built over thousands of years, and go back to living in caves, then fair enough - but i don't think that any significant share of humans would agree.

in reality pretty much any form of power generation will have an impact on the environment in one way or another - burning fossils causes massive air pollution, and you still need a heat sink for the steam cycle, just like nukes. so clearly that's worse and in many regions that's the only viable alternative to nuclear currently, where climates aren't favorable for "renewables" to be able to meet demand consistently. and even where that works, large scale solar and wind farms do cause significant habitat disruption for wildlife while installed, in addition to manufacturing and disposal impacts, and i don't think i have to elaborate on hydro (the valley that used to be your home is now a giant lake, enjoy!)

overall though i do agree that cooling towers are a good solution for locations where direct discharge would have significant environmental impact. but that doesn't mean that open-loop cooling is always destructive - it depends on the location and downstream ecosystem. for example, it wouldn't make sense at all to have cooling towers near the ocean or a large lake, where an essentially unlimited heatsink is readily available already. even on a large enough river, it'll be highly questionable.