You are disingenuously, or erroneously, mixing up terms which have different meanings. Trump was patently not particularly qualified to be President - he had no prior experience in public service, foreign affairs, domestic affairs, political negotiations, military experience or any of the other common qualifying life experiences generally considered relevant to the Presidency. Since assuming office he has amply demonstrated a complete lack of ability in handling the responsibilities of the Presidency. Nevertheless, he WAS elected President. Thats because the President is primarily a political figure & Trump showed some political skill at persuading a portion of the American electorate to vote for him.
With a long career in public service & politics Biden clearly has more qualifications when it comes to the Presidency than Trump did. Whether he has more ability remains to be seen. Regardless, Biden's choice of a VP is a first & foremost a political decision, just as in the case of every previous VP choice, from LBJ to Sarah Palin to Mike Pence. Biden has made the political calculation that the timing is right for him to choose a woman & possibly a woman of colour (although that has not been explicitly stated) as his VP. There are plenty of women with the qualifications & presumed ability to handle the role. It's hard to see how any of them are likely to make a bigger hash of it that Trump has of his Presidency.