none of the actual predictions made over these years by the "alarmists" have ever materialized.
I don't know about none, there's probably one or two somewhere that have come true but essentially, yes, you're right. None of the claims made by the alarmist have come true.
On the other hand, scientists tend to be conservative and like to make predictions that are backed by a good understanding of what is happening. This is resulting in things typically being worse than the predictions that scientists were making.
In the 80s when I first became aware of the problem of CO2 in the atmosphere and the greenhouse effect, scientists were talking about hundreds of years for the Arctic to become ice free in summer. By 2000 they were talking about 2050. 2015 and 2035ish seems to be a point where the money is going. (My guess from extrapolating what the reasoned voices are saying is that the first exceptional melt year after 2020 will do it after which it will rebound for a few years and then we'll have ice free summers theafter)
I've not really followed Antarctica. However, back in the 80s I'm pretty sure it was "tens of millenia to melt all of Antarctica if it's possible at all". More recently I've seen comments along the lines of "It can't happen in less than 5-10 thousand years" with the assumption that it will happen eventually if we continue dumping CO2 into the atmosphere.