Newsflash: It’s entirely possible to believe that Pelosi should not be Speaker without being a sexist. Especially given that the opposition extends to the entire leadership team (mostly men). The fact that her supporters are using sexism to guilt Democrats into voting for her is s sign of how worried they are that she won’t secure enough votes.
But what I find to be especially ridiculous is the claim the Pelosi deserves to be Speaker because she delivered the House majority to Democrats. There are several problems with this argument: 1) If she’s responsible for the 2018 win, then isn’t she responsible for the 2010, 2012, 2014, and 2016 failure to win the House? Why credit now and no blame then? 2) No one credibly claimed that John Boehner won Republicans the majority in 2010. It was Barack Obama who delivered the House majority to the GOP in 2010. 3) If the Speakership should go to the person responsible for Democrats winning the majority, then Donald Trump should be Speaker. He's the one who drove college educated suburban Republicans away from their party.
Democrats need to embrace a new generation of leadership. The problem being that that new leadership must come from the party’s center - and there is no clear candidate. Democrats won the majority because of the success of moderate candidates in the suburbs once dominated by the GOP. The recent threat by Ocasio-Cortez to recruit progressive candidates to challenge incumbent moderate Democrats is a surefire recipe for becoming the minority party again.