It's possible all the experts are stupid, or that you don't have as deep an understanding of the situation as they do. Which is more likely? That may come across as glib, but seriously, occasionally when it seems like the expert consensus makes no sense, it indeed doesn't. Most of the time though it's just that you don't have the necessary knowledge and experience to effectively evaluate the expert position.
In this case, yes, as people are vaccinated, variants that evade vaccines will spread more easily than others. From what we've seen so far, these same variants tend to be more contagious regardless, so that likely would have been the case anyway. By vaccinating though, you achieve a few things. First, you protect people from the variants that are susceptible, saving a lot of lives in the short term. Second, you massively cut down transmissions of the virus, each of which gives it an opportunity to mutate and produce new variants. Third, in most cases, you do provide some protection even against resistant variants.
And finally, just as the virus is not static, neither will be the vaccines. Work is already underway to update all the major vaccines to cover the new variants, and that process should be much faster than creating the initial vaccines (in design, trials, and roll-out). So it will be possible to vaccinate against variants that evade current vaccines.
Yes, it will take a while, and it would be nice if the virus would just sit still and not mutate. But we're still far, far better off with vaccines than without them. You are correct though that other measures will need to remain in place for some time as well.