Complaining about parking is useless. Every single city I have lived in thinks they have a parking problem. People that complain about parking because their business is not successful need to acknowledge that there are bigger problems than parking. The problem of a failing downtown is that there is really not that much downtown that is worth the effort of going there. If you focus on creating a place people want to go, more likely than not, people will figure out the transportation issue.
For example, parking is the number one complaint about downtown Conway, Arkansas. Yet, the city closes off the main street for a weekend for their annual festival, and the organizers claim 100,000 people from around the region turn up;
They parked at a friend's house, they parked a couple of blocks over and walked. If you create a place people want to go, these things happen to solve themselves. The same thing happened in Hoboken, New Jersey several weeks ago.
You need an anchor that draws people in. In this case, the festival was the anchor. Parking is not an anchor, nobody says "I am going to visit this parking spot!" Parking is a tool, just like your traffic lights, your bus stations, etc. as a way for people to get to the anchor.
The anchor does not have to be one specific building (if your town's only supermarket was downtown, people would figure out a way to get downtown when they needed to go to buy groceries), but the environment in general. For example, one night, I ate out with my parents in Little Italy, we had this view;
We could have gone up to any Italian restaurant up the street for a decent meal, but it would not have the charm of being in cozy Little Italy, so we went 35 minutes out of the way for dinner. You can not get that atmosphere in the suburbs. If our street is dead, we need to take a holistic view of the street to say why people do not want to go there. (Is the streetscape pleasant and unique? Are the countless things to do once you are there?)
If we really fall for our own false belief that parking is the problem, what is easiest "solution"? Knock down buildings for more parking? The problem is, for each less building we have 1 less reason to go downtown, and people will still complain about parking. So we chase our tails more, and end up with one or two buildings per block, surrounded by parking:
The end game of this approach is that you end up with a crummy imitation of the suburbs that is both unpleasant to walk and unpleasant to drive, few to no anchors to draw the people in, rents will fall because there is nobody walking around, and you have cannibalized your own city.
The question we should be asking is not "What can we do to make it easier to come downtown?" but "What can we do to give people a reason to come downtown?"