Nope, because of much lower mortality of delta variant independent of vaccination rate. Public Health England reported that the Delta variant in England had a case fatality rate (CFR) of 0.2%, while the Alpha variant's case fatality rate was 1.9%. It's also visible on global mortality rates, once delta variant became prevalent. See also:
Kids and the Delta Variant: Should you Act Differently? Several studies out of the UK showed extremely low child death rates. Of almost half a million infections, there were 25 deaths, 15 of which were in children with serious underlying illness. The hospitalization rate of coronavirus - while already low for children - dropped to nearly zero for kids at the case of delta variant. Corona has a lower death rate than flu/pneumonia in children.
LOL
You are double-counting here. The low CFR of delta in the UK - and many other places - is because of the vaccine!
(In some underveloped countries it is due to lack of proper death counting - e.g. in Uttar Pradesh in india there has been a mysterious rash of fever deaths throughout the Province not counted as deaths, and in towns the reports from those running cemetaries are completely inconsistent with official COVID deaths by a factor of 10).
Your argument about children is a different one - there have been very low death rates for original, alpha, and delta COVID. The best research on delta deadliness is as I said - double of original, a bit worse than alpha. Which you would expect, given what we know about its differences.
I'd also caution you to use CFR as a proxy measure for IFR with great care. In many places (e.g. some parts of India) there is known undercounting of both cases and deaths - both by a lot. So CFR becomes almost meaningless. Even in most places where deaths are well counted, cases are not always related to infections because they depend on the level of testing. The UK first wave dramatically undercounted cases because of a lack of testing. Many other countries have the same effect. So look at the amount of testing and the test positivity rates, and the seroprevalence surverys, and put it all together (as the ONS data does in the UK) before coming to conclusions about IFR - e.g. how deadly is the vaccine.
And then look at how much of the at risk population is vaccinated!
Please look at the data with curiosity and engagement? All of the data here fits together, to understand it you need to take a bit of time and ask questions. I will help. Sometimes it is uncertain, which is why I stick to the UK where we have exceptionally high quality data from the ONS infection survey.