It's simply not that effective, it has a very small treatment effect and isn't a great tool, but it's certainly much more justifiable than hydroxychloroquine, which took much of the oxygen out of the room when POTUS and the GOP hyped it FAR beyond its statistically shown merits.
Also: it has serious manufacturability issues, and it can only be administered by IV.
It’s entirely plausible that giving remdesivir to COVID-19 patients when they first show symptoms would make a big difference, but it’s impractical.
"The most common adverse effects in studies of remdesivir for COVID‑19 include respiratory failure and organ impairment..." —wikipedia entry
That sounds more like "sometimes it doesn't work" than "sometimes it extra kills you".