Where exactly are these "major" security issues? Even one of the researchers involved doesn't seem to think this is "major"..... In fact, he even goes so far as to say that it's not "major" and "leaks a few bits of meta-data" compared to Meltdown leaking actual, usable data. Meta-data, for the most part, is useless to attackers. The actual data, as made available by Meltdown, is vastly more important and useful.
Each of these 2 flaws, requires multiple exploits......so, not "simple to exploit".... Unlike Meltdown, that accomplishes more, with less and is much easier to execute. If you read the paper, there are a total of 4 exploits discussed. For a "few bits of meta-data", you have to execute 2 different exploits. This isn't something an attacker is going to do for "a few bits of meta-data"......