For the CBS owned stations, I think comes down to a lack of budget and the resulting lack of identity. CBS O&Os historically have spent less than their ABC and NBC counterparts leaving them with fewer resources. To play catchup stations like WCBS and WBBM have gone through numerous rebrandings.
From a corporate standpoint, CBS has undervalued the "presentation" portion of TV news which has been reflected in the way they fund their local stations. They live in the Walter Cronkite era of storytelling. Admirable? Sure. But television is a visual medium and newscasts are built on a relationship with the viewer. I don't feel like CBS has ever truly embraced either of those things. The lack of investment was easier to hide in the 70s and 80s because everyone's presentation was crude. But as technology has evolved, CBS always seems to be playing catch-up.
When Jeff Zucker cut NBC budgets in the early 2000s, WNBC went into their "WCBS era" where they lacked identity and money. The NBC O&O group launched Daily Connection which was a "newscast" that featured repurposed content from across NBCU properties. The pieces of the show were assembled in NYC and then fed to stations to be produced with local talent. (Sound similar to the equally generic CBS News Now broadcast from Texas?) Cost efficient? You bet. Compelling tv? Not at all.
WNBC eliminated Live at Five in favor of News4You and Extra. When that didn't work, WNBC played musical chairs with timeslots, anchors, and formats for years. WNBC their newsroom into a "Content Center" which was nothing more than a gimmick, like the gimmick WCBS tried in launching the short-lived CBS 2 Information Network. It was during this time when WCBS was able to move up to #2, not because Channel 2 was doing anything particularly compelling but because they offered stability where WNBC didn't.
Valari Staab, formerly with the ABC O&O group, has spent over a decade rebuilding the newsgathering resources of the NBC group. New radar technology, studios, increased digital resources, heck even new buildings have been added. CBS meanwhile appears to continue the "more with less" mantra that has been in place for over 40 years. While NBC was rebuilding, the ABC stations, with their well-defined local identities, have steamrolled everyone with a consistent and well-funded product. Meanwhile the FOX O&O group, with seemingly endless hours of local news, generates strong local revenue.
What has CBS done? Slapped the last-place 'CBS News' brand onto their local stations. Most of the CBS stations lack the type of true community investment it takes to be a strong player. With audiences for linear TV newscasts continuing to shrink, one could argue it Is way too late for them to catch up.