You may be right. I can't find exact statistics, but I saw a few sites giving numbers of 20,000 - 30,000 (for Afghanistan). The rate of children being killed in Gaza however is far more.
A quick Googling doesn't find me a counter-estimate from Israel. Given the very clear evidence of large scale bombardment of the Gaza Strip (Israel claims 6,000 bombs dropped, and Hamas is known for favoring populated areas; https://www.wsj.com/livecoverage/israel-hamas-war-gaza-strip...), counts in the thousands seem very plausible.
They've already botched major events, like the death toll from PIJ's accidental strike on Al-Ahli Hospital. There's also an ongoing concern about "Gaza Health's" practice of including Hamas fighters in civilian death tolls. They're the best numbers we have or are going to get, so they can't be ignore, but their reliability is probably not a good hill to die on.
Israel's had its own counting issues. It's a challenging enough task with a functioning government and control over the area, let alone an area with more than an a million evacuees going in various directions. https://www.wsj.com/livecoverage/israel-hamas-war-gaza-strip...
I don't doubt they include Hamas fighters, but I do doubt that Israel's targeting has been so effective and precise the deaths are mostly Hamas. US intelligence estimates 20-25k Hamas members (https://www.dni.gov/nctc/ftos/hamas_fto.html); I don't think half of them are likely to have been already taken out.