The problem is not just lack of liquidity. If that was the case, the simple solution would be to just print a bunch more money. Then people would have more cash laying around, more of it would end up in banks, which would allow banks to extend more credit.
However, this is unlikely to be the root of the problem. More likely is that the national economy is simply not productive enough to reach the production levels needed to enjoy prosperity similar to the one observed in developed countries. What that means is that on the one hand, too much of existing production is going into consumption, and too little into investment. Instead of building more houses, they should be building more cement plants, more building material factories etc, and the same goes for other sectors of economy too (eg if agriculture mechanization allows fewer people to work on food production, more people will be available to work on house construction). Of course, given the already low levels of production and consumption, it’s hard to reduce consumption even further, but then again, prosperous western countries used to be just as poor in the past, and they managed to pull themselves by their bootstraps anyway. In many ways, African countries today have it easier, as the knowledge of what to do and how already exists.
In addition to too scarce investment, a second major factor is differences in productivity on individual worker level. The sources of these differences are really diverse: they range from bad people management practices, through use of inefficient work techniques, higher human error rates resulting in more time wasted on useless products, and many more. This is a harder problem, and there are no simple solutions, but on the bright side, the longer economy is stable, the more companies have time to mature and refine their practices, so this is improving on its own over time.
And lastly, there is often problem of bad institutional practices, like excessive taxation, excessive regulation, government corruption etc. It’s much easier to build a cement factory when you don’t have to care much about environmental regulations, and this is exactly the regulatory regime that countries like Britain, US or China enjoyed when they were climbing themselves out of poverty. Similarly, there is more money for investment, if the government is taking less of it. This sounds like something easy to change, but in practice the institutional inertia, combined with copying Western practices as of right now rather than as of when they were of similar development levels makes it harder than it should be.