If that were true, teams would never sign their kickers to extensions. They would just sign someone who just got their diploma.
Kickers overall have gotten better, but the league is going thru a stretch where finding a quality reliable consistent one is easier said than done. They usually take a bit of development.

This year there really wasn't cap space or lofty expectations, so having a young kicker work out the kinks isn't the worst thing... assuming he works out the kinks. I think Carlson absolutely needs to improve, and I also think the team needs to bring in camp competition.

The SF playoff loss did not hinge solely on a missed FG. There was dropped Savage Int, a bad 4th & 1 spot, a bad final Int by Jordan Love, and a few other plays that were just as critical. SF's K had one blocked, nobody is going to run him out of town for that.