The left wants SCOTUS, and with it the whole Constitution. The left would love to control a convention and a ratification - which would accomplish the same thing as controlling SCOTUS, and possibly even more. But, IMHO, the left stands a much better chance of controlling SCOTUS than it does of ratifying a bad amendment, even assuming they could get such out of convention.
Robert Michels' Iron Law of Oligarchy states that in any organization the permanent officials will gradually obtain such influence that its day-to-day program will increasingly reflect their interests rather than its own stated philosophy. That is simply another way of saying that there are amendments which should be proposed, but which Congress itself would never propose - by even so much as a majority, never mind by 2/3 in both houses.
The salient example of which is Term Limits on Congress. You notice that there is a term limit on the president, passed by the first Republican Congress after the Roosevelt Administration and ratified in 1951. No doubt there have since been presidents who would have proposed to the states that term limits be imposed on Congress - but, obviously, there has never been a Congress which proposed any such thing.
Speaking of SCOTUS, the life tenure thing is not entirely satisfactory. I would propose, were I in charge, that a new justice be named every two years, and that the size of the bench be set at eleven justices (rather than, as at present, at the whim of Congress). I would eliminate the filibuster for SCOTUS justices who had been named as candidates prior to the election of the president nominating them. Each two-term POTUS would then leave a legacy of no less than four elevenths of the justices on SCOTUS, and only rarely more. Justices would retire after 22 years on the bench.
Ratification of nominees to SCOTUS would still be a problem if the Senate were not controlled by the party of the president; the Seventeenth Amendment eviscerates the rationale for the Senate as representing the states (instead they represent the people of the states), so I would propose that confirmation of justices either be dispensed with (in effect being done by the Electoral College) or be ratified by the state legislatures instead of the Senate. If the latter, it should be the default that the nominee be confirmed, and action by a majority of the state legislatures be required to veto a nominee. If SCOTUS is going to be reinventing the Constitution with things like Roe v. Wade, the state governments should insist on having a say-so as to who gets on SCOTUS.
A majority of state legislatures should be able to nullify the precedent value of any SCOTUS decision (or non-decision, in case of a tie). And the states should be able to Recall a SCOTUS justice after nullifying three (say) SCOTUS precedents set by such justice.
The illustrated Amendment XXIX in #24 addresses all of the concerns you raise. It is simple and its products can be executed completely outside the purview of any federal entity.