I think it also reflects that Klentak thinks he's still rebuilding this team, and overspending for a rental to win 2 more games down the stretch doesn't fit their long-term strategy right now - if this was 2020, the lineup was set, prospects were blocked and they had a shot at the WS I suspect a different decision would have been made.
They're in the situation where the only way they make a deep run is if the kids step up, but they don't know which kids might step up - so they don't know where they want to make improvements. That is, they want to play Crawford, Kingery and Franco, and hope 2 step up and take jobs - in which case the lineup is improved and they might contend. In the same way, they'd like to see Williams/Altherr pick it up the second half, same with Alfaro/Knapp. Once the lineup is set, prospects unlikely to crack that lineup in a couple years become prime trade bait.
The rental makes more sense in the case of a team like the 2008 Phillies, where upgrading Feliz or adding pitching depth would have been a good move (if they had farm system depth like they have today). That team overachieved, but the next three seasons better teams underachieved - go figure - or why you try to remain competitive as long as possible and hope the Baseball Gods smile upon you.
