Most buses stop almost every block, they board through a single door, and they use the two slowest payment methods available in almost any system (cash and magnetic strip cards).
However, I don't expect this to change anytime soon, because many existing riders are very invested in keeping buses the way they are. To be clear, their concerns are valid - for a variety of reasons, it may be difficult for many people to walk an additional block to their local bus stop, vs. having a stop in front of their building. Many of the current riders are also long-time residents who are more likely to go to community board meetings, contact their city council members, and protest changes in other ways. If you're a policymaker, it's hard to weight the costs that would be imposed on this vocal set of people vs. the benefits that would accrue to a much less vocal group of people who would benefit from a faster and more consistent bus.