Are index futures worthless?

I've been observing stock futures for the last month, and they've been completely off from how the market opens 9 out of 10 times. Look at today for example, Nasdaq futures down over -1.00%, and still down -0.45% ahead of the opening. Nasdaq almost positive 3 minutes after opening. The inverse happening is also very common, if futures are up, stocks will open down. There is no rhyme or reason for this, tariff reactions from Friday were muted, and if anything market should be down further after Warsh's hawkish comments today. Why is this the case? Are futures 30 minutes before open really that illiquid compared to a broader open-market?