It looks like you’re correct about the present-tense, but it doesn’t actually change the argument. When people blast the Dem’s political leadership for being spineless it’s often directed at long term figures of the party, like the Clintons, Biden, etc. For the vast, vast majority of those politicians careers the Democrats were not >50% liberal (a number that on researching it further, appears to have not happened until 2018.) There’s also little evidence to me that most of these politicians were “closet leftists who pretended to be centrists.”
To me, it’s spineless to pretend to be someone you’re not because you’d rather have a cushy government job than stand up for your actual political beliefs. I see very little evidence guys like Biden, either of the Clintons, Pelosi, Senator Chuck, Steny Hoyer etc are secretly ultra-liberals and have just been pretending different for decades. These people largely reflect a very mainstream set of positions within the Democratic party, even if those positions may not be mainstream on the (infamously leftist) SDMB, or other far left internet communities like Daily Kos etc.
I point to someone like Mitt Romney as my example of spineless because he appears to have no meaningful political positions. When he tried to beat Ted Kennedy for Senate in the early 90s in Massachusetts he was quick to defend himself as pro-choice, and had a number of other frankly liberal positions. Was that the real Mitt? I don’t know, it’d be weird for someone raised in a traditional Mormon household to be pro-choice, but maybe it was. But that Mitt later ran for Governor of Massachusetts and ran Massachusetts for four years. Then later had two runs for President, during which he magically shifted on healthcare, abortion, and almost every other meaningful political position he has ever held. I don’t believe that was a “genuine evolution”, I think that is spineless political opportunism.
Can you find that in the Democratic party? Sure. But I struggle to identify any of the major, national-figure Democrats who really fit that definition. I’d suggest maybe Bill Clinton does, because he actually had a history before he was President of being at least outwardly fairly liberal (although this wasn’t dramatically reflected by his actual actions as Arkansas Governor, and after the 1994 Midterms all of his rhetoric permanently shifted rightward.) Hillary on the other hand had a pretty consistent set of policy positions, some of which she maintained as First Lady in spite of them probably costing her politically, and she only gradually changed them over many years, generally following a process through which many Americans changed their opinions over time. That’s a real process–America didn’t go from thinking of gay marriage as an aberrant monstrosity in the 90s to mostly accepting it in the 2010s because literally all the old people died, a huge portion of the country had a genuine change of heart on the topic. The various crime bills represent a similar issue, a lot of younger people probably don’t remember it but crime was genuinely very high in the 70s and 80s and into the early 90s, before it started its famous, long decline. Crime was promoted as a catastrophic thing in our country, on the nightly news, all the “news magazine” shows like 20/20, 60 Minutes, it felt like half the TV shows of the 80s/early 90s were crime shows set in the major cities, which were frequently depicted as dystopian hellscapes. A huge portion of the country was outraged about crime and severely angered by what they saw as an overly lax criminal justice system. It’s not at all surprising that politicians of the time would have shared similar views and acted accordingly.
It’s also not surprising as higher quality sociological/terminological research has been done, as the consequences of these actions have been examined over the following decades, that people have a natural shift in positions. I don’t think Biden was spineless for supporting the heavy handed criminal justice reforms of the 90s because most of the country genuinely thought they were necessary and proper. I don’t think he’s spineless for going back on his views 30 years later, because most of the country has had a chance to learn better.
I would also warn when you say most of the country wants “liberal policies”, you need to actually dig a little deeper into the reality on that. Medicare for All is remarkable in how well it polls when people know the least about it, before even addressing that it would entail people losing their private insurance, if you just mention it will raise taxes, support for it falls to the mid-30s/low-40s in various polls, making it not even a majority position anymore. Slavery reparations I think are opposed by something like 80% of White America, which is the kind of number that means you’re angering more people than you can afford to anger and still win a national campaign in the electoral college–food for thought, the GOP doesn’t plan to let you guys keep the details vague on these things.