For one thing, the scores are based on a metric established by an organization that has its own political agenda. That's OK, but in some cases the "good" score on their scale may be diametrically opposed to what I think is a sound political philosophy.
For example, some of these ratings systems are set up in such a way that an open-borders, "free trade" advocate will score higher than a MAGA-type who advocates strict immigration controls and protectionist tariffs.
And there are always those members of Congress who will never stay in office if they vote against certain bills that benefit key industries in their own jurisdictions (think Lindsey Graham with Boeing Corp., Charles Grassley with Archer Daniels Midland, Mitt Romney with Jockey Underwear /just kidding/, etc.)
“For one thing, the scores are based on a metric established by an organization that has its own political agenda.”
You’re correct. I used to compile an average for Republican senators. I would take all the scores and average them out to get a REAL rating. For example, John McCain had a “lifetime” ACU (American Conservative Union) score of like 90%, which meant that all McCain would have to do is vote right on taxes and abortion and score high. And he would vote liberal on everything else (that is, everything else not rated by the ACU).
The score was a total sham. But when combined with all the others McCain went from about 90% down to like 58% if that.
Having said that, I think CR has the best and most accurate scores.