Okay, you should be aware that that study you're referring to the numbers of, was done by iirc a scientist linked to a Venezuelan thinktank whose stated purpose is sanctions relief. The study itself also has some questionable methods, for example: if a country previously provided aid in some form, but then stopped, this is counted as a "sanction" and any loss of life is thus included in the figure. So suppose country A supports country B with some aid program, but then B has a violent military coup. A now stops the aid, as there are clear signs that the junta in B is seizing the resources for themselves. The potential deaths the aid could have prevented when the aid was effectively being administered are included in the calculation for a period when that aid more than likely couldn't be effectively administered. Aid programs with a limited duration are also included as "sanctions" once the programs end.

This inflates the numbers in quite a big way. Of course it's still horrid that thousands die due to sanctions, but those numbers don't paint an accurate image (this is not to discount the entire study btw, but it's important to be aware of the nuance here).

Then there's the question of: what is the alternative? Doing nothing at all? Declaring war? Sanctions do have an effect after all. Take apartheid South-Africa, eventually apartheid fell due to the severe economic pressure from international sanctions, spearheaded by India at the time. You'll also have to ask yourself how many more people in SA would have suffered and died if no sanctions had been instated and apartheid had been allowed to fester unopposed internationally. And this effect was never taken into account into the study either.

Of course you could also hypothetically attribute the deaths to whatever triggered the instatement of the sanctions in the first place. If country A declares a war and gets sanctioned because of it, are the extra deaths in country A on the hands of A's government or on the international community applying sanctions?

There's plenty of ideologically motivated sanctions, especially levied by the US, that are total bullshit and just harmful (see: Cuba). I'll always oppose those.