VPs rarely ever deliver states anymore, the effect is very small. Indiana was going for the Republican nominee in 2016 no matter what (although it was a surprise in the Obama 2008 coalition). Ironically California (Harris) balances Delaware (Biden) quite well in terms of geographic spread which is sometimes desirable. Harris is the first member of the most populous state in the nation on either party’s ticket since Reagan 40 years ago!
Harris balances Biden most importantly in age and identify, both of which are important in the Democratic Party. She’s also a credible President on day 1, as was Pence, which IMHO is the very most important criteria for a VP.
On age, Biden (and Trump! and Hillary!) are all IMHO too old to be a President who could win and govern through two terms with all their marbles intact. Not everyone believes that but I do at least. 45-65 is my strike zone for a President or other high level leader and ideally they’d all be done and retire by age 70, i.e. don’t run for a first term if you’re already over age 62. Biden is 77 and Harris is 55 and she’s already been in the Senate since 2017 after working her way though other high-level state offices - good balance.
In terms of identity, the Democratic Party still has a lot of white male leaders while white males are a minority of typical party voters, so it was important in a big-picture sense to have more leaders who are women, people of color, or both. It’s not about “racism” or “sexism,” but representation and making an effort to have our party leadership look like the party membership. Stating the obvious, she is a she, she’s black and Indian, and the daughter of two immigrants. He is a he, white, and of longer American-born lineage - good balance.