PMQ's isn't about swaying public opinion, its about formulating the media narrative. All those political journalists from all sides are watching it weekly, and watching Boris look like a fumbling fool who is getting eviscerated week after week by a calm, calculating Starmer. That then effects their perceptions and how they report political news.
As for 'in a few years' all that is just speculation and supposition. The Tories have been in power for a decade now and the same things are happening to them that happen to all governments who stay in power too long. Corruption seeps in, incompetent people rise to powerful positions via cronyism and the whole thing starts to creak at the seams. The Tories can't just reinvent themselves, because it would require the whole party to change, and that simply isn't going to happen.