Actually, the speed is not the problem. Everyone can cope with it. Besides, Lightning Network is present which could fix the problem.

I think the main problem why bitcoin is still far away from the mainstream is because of technological illiteracy. Huge portion of our population are still mot aware about this so educating others would be very important factor to consider. Another reason is that people are into fiat, they feel contented with it already thus refuse to explore other means. Nonetheless, our community keeps on growing little by little and that's good.