This is just more overreacting to a slump. This happens every time the guy struggles at the start of the season, and the various detractors are always quick to make immediate declarations that the slumping version of this player represents his offensive upside. Conversely when he goes on an extended run of offensive success it's completely crickets time from the haters with nary a peep to be made about the success. Biggio is struggling at the plate, that's impossible to deny, but at the same time if he turns things around he has potential to once again be a very solid contributor. After his swing change last season he was the team's 4th most productive offensive contributor among regular players for 2/3 of the regular season, outproducing the likes of Vlad, Bo, Kirk, Springer, Merrifield, Chapman and Espinal. He was far from the reason the team struggled offensively as he produced much better quality of contact metrics and actually earned his offensive numbers and playing time by effectively swinging the bat. He produced a 124 wRC+ and 1.4 FWAR in 272 PA. That is a quality major league player as he produced value akin to a 3 win player if averaged out to a full season of plate appearances. He earned himself another look this season through good play.
If he doesn't turn things around it's not like it's hard to simply allot more playing time to someone else, and if someone else eventually takes his place so be it. It's entirely possible someone like Barger eventually kicks the door in and takes the corner outfield spot, and the likes of Clement or IKF eventually render him as completely expendable, but that hasn't actually happened yet as it's up in the air what kind of offensive contributor Clement eventually settles in as over time, and IKF doesn't exactly have a track record of exemplary offensive production that makes him a shoe in to continue producing the way he has up until this point.