That's not what entryism is. Entryism isn't "voting democrat candidates who support xyz in primaries." Entryism is infiltrating an organization's membership with communists(or what have you), with the intent to change the basic proportional makeup of its membership ranks, and so change its interior political composition, and so its exterior action.
Entryism is explicitly and categorically denounced by every serious ML as having proven historically and politically ineffective at best, and actively counterproductive and opportunist at worst and most common by far; and has been in explicit terms criticized as such for a century. Saying "Surely you've heard of entryism?" to Marxists is like saying "Surely you've heard of filling masks with lavender to keep away the miasma?" to an epidemiologist.
The point mentioned in #2 is by a factor of 100 extra true for an organization like the democratic party, which is (just like the Republican party) a monstrous behemoth of leagues of multi-generational dynastic establishment careerist ghouls, thieves, racketeers, and murderers from multi-billionaire elite university family empires; whose entire operations are financed, advised, organized, and run by and for the richest imperialists in the world, with uncountable streams of both open channel money and dark money from private billionaires, banks, industrial monopolies (fossil fuels, pharma, agribusiness, etc.), arms dealers, conglomerate Super PACS, shady Think-tanks and "NGOs," and the Israel lobby. Obama's cabinet was hand-picked by Citigroup. Biden has appointed all the most heinous neocons and war criminals he could find, even bringing back convicted massacrists like Elliot Abrams; and hiring the most corrupt people he could find, such as a Chevron lawyer who defended the destruction of the Amazon and poisoning of Indigenous people to head his Environmental executive. All while outflanking the Republicans on the right of many issues including immigration.

The Democrats actively benefit just like the Republicans from hyper-restricted 2-corporate-party system, proven by them, currently as we speak, sending out leagues of dark-money Super-PAC-financed lawyers to every state they can to try to purge 3rd parties off the ballots; actively killing democracy. This is their goal and interest, because it is the goal and interest of their donors. They have no interest in a different or better world and never will. Even someone as milquetoast as Bernie ran into endless smears and obstruction and undermining and got nowhere and has capitulated more and more to the right wing by hitching his boat to this circus. The liberal darlings "the squad" have each capitulated or even become active careerists and attack-dogs for the establishment imperialists against alternatives and progressives, barring Ilhan Omar who has faced endless shit and isolation even from the rest of that coward group of "progressive" dems, to say nothing of the establishment that actually runs the show with their army of equally-careerist factory-stamped liberal interns at their beck and call, pipelined from upscale colleges with PoliSci degrees to do whatever bidding they want.

The Democrats are not going to change for anyone but their donors and have proven it for decades; and they are structurally incapable of being budged internally toward anything remotely resembling democracy or socialism. Entryism to the democratic party is beyond a dead end. It would It would be more effective and principled to vote third party and continually elevate a working class party (Like the PSL) and visibly starve the democrats of votes for their failures and betrayals and making it known that is the reason; which would force a political reorientation of the democrats if they ever want power again. This necessary reorientation is impossible within the Democratic party structures, so the ruling class would have to figure out to desperately float a reformist "labor party" or "progressive party" to capture people being funneled to the PSL socialists, and this reformist party would receive an influx of the less-far-right careerist liberals from the Democrats fleeing to the new party "like rats from a sinking ship;" while the Republicans and remaining establishment Democrats proper inevitably join together in a coalition like David Lloyd George's Conservative-Liberal coalition, or like Macron's doing with the fascists in France. It's not even much of a leap for them compared to the existent state of things

they've already been converging for decades and most of us have already come to feel the effects of it.

And this way by elevating the PSL, a real working class party who have a broader picture for revolutionary change than limiting to parliamentary dog-and-pony shows against the richest most evil people on the planet, you're actually helping the ground-up elevation of meaningful on-the-ground working class politics which speak to the 35-50% who are so disillusioned and disenfranchised by the lies and corruption and bloodthirst of the corporate-imperialist duopoly-of-exploiters that they don't even vote

and activating them into actual meaningful political movement-building and action with a revolutionary long-term perspective, while forcing the establishment's hand to intercede how it can, highlighting the contradictions and failures of the system. Instead of finding new ways to capitulate to it (which are actually the same ways people have been capitulating to it for a century).