I've seen this take a lot that anyone can master anything if they just try long enough. People cam get good at many things, but we don't all progress at the same rate. Nature and nurture both have very important contributions to make.
There have been men who have worked at composing their whole lives who never got as good as Mozart by the time he was twenty. Maybe they didn't try hard enough?
OP, how long since you bought toothpaste before this one bum tube? Has it been so long that you have to contemplate if we've entered a new era of toothpaste tube quality?
Some toothpastes have calcium in them as an abrasive, and the fluoride will become bound to calcium over time. In that state, it's not able to strengthen your enamel. What I'm saying is that toothpaste may have a shelf-life, so you should be buying it bit more often.