I never mentioned sedans- I said "rent a suitable vehicle", which is invariably a diesel truck.
Sure, you can do a road trip in Africa with an SUV- provided you don't venture too far (50 -100 km) from major centres. The roads around most major cities are generally in reasonable condition, but anything beyond about 100 km or so from a major city (and considerably less in some cases) becomes an overland expedition to the next major city.
If you don't want to do cities, any distance between two points in Africa is an overland expedition, and especially so in central Africa, where nobody has been able to build permanent roads- or railways for that matter. However, large sections of the Trans-African Highway system (the parts of it that run around the edges of the continent, at least) have been paved and/or upgraded during the past ten years or so, but there are no guarantees that any part of the Trans-African Highway system will remain paved from one year to the next.
If you ever end up in washed out section of the road system in the dry season, when big trucks have reduced it to series of deep trenches that can be deeper than a meter, and run for tens of kilometers, you will find that the limited suspension articulation of an SUV- any SUV- will leave you crested on these trench tops every few meters. Then again,if you ever end up in a washed out section of the road system in the wet season, you need to be in a group of at least four trucks to get through meter-deep mud traps that can run for tens of kilometers. If you can get past the dozens of big trucks that have been bogged down for months in a track that is barely wide enough to allow two ox-carts to pass each other, that is.
In fact, a few years ago I had to abandon one of my expedition grade vehicles in such a mud trap because there was no way to get it out of the mud from behind an 18- wheeler that had sunk into the mud up to the top of it's wheels, and from in front of another 18-wheeler that had followed me into the mud trap before the other vehicles in my expedition could follow me in. For all I know, both trucks and my vehicle are still stuck there.
So, no, SUV's without proper 4-wheel drive, low range, winches, lockable diffs, rated recovery points, and at least 28 inches of suspension articulation in Africa are not good idea if you venture away from the big centers.