This comment demonstrates both confusion of the Dyson sphere concept with it's sci-fi bastardisation as well as a lack of understanding of scale, and especially of the mechanics of black hole power production. Dyson spheres (or Dyson swarms as they are often called to prevent such confusion) were never originally envisioned as a single impossibly large rigid sphere encompassing a star. They are rather a massive collection of structures that are able to utilize all the energy output of a star. This means that you could start construction on one today in an iterative fashion and immediately benefit from it.
The technology required to build a tier 1 swarm is not advanced. All you need is the ability to build a thin reflector (aluminium foil would work) with radio and a basic onboard computer. You do not even need onboard propellant because a reflector can generate the required thrust for minor corrections with solar pressure alone. These reflectors can then concentrate that light from close in to the star out to collectors further out in the system. This essentially makes your habitable zone as large as you want since you can also light entire planets this way and only utilize less than a percent of a percent of your total energy budget.
The real challenge is having good enough automation to construct and send these stations out without requiring too much oversight, and getting good enough at construction off earth (since you really don't want to deal with that gravity well). We're definitely close to having the required automation technology and we should be performing the first manufacturing off earth before the end of the next decade.
Artificial fusion can be made far more efficient than the fusion in the core of our sun, yes. However, the sun outputs enough energy to light 2 billion earths worth of surface. Moreover, it essentially contains all of both the hydrogen and rocky material in the solar system with the other bodies being essentially a rounding error in comparison, so even in a controlled fusion based economy, you would still create a Dyson sphere like construct since you would be using that star as your main fuel and mass source.
Black holes though? They make even aneutronic fusion look like a fire cracker in comparison. You're getting less than a percent mass energy conversion with even the best theoretical fusion models there are, whereas with black holes, you can get anywhere from 16% to 40% depending on the technique and mass range of the black hole. Stellar black holes have so much energy inside that they would dwarf even our star (consider that their progenitors were stars with far more mass than our own and with an even bigger disparity in power output). They also last for periods of time that make even red dwarfs look like still births. If you could make artificial ones in the gigaton and megaton ranges, then they can also make for amazing batteries. In this case, you are able to tap the hawking radiation emitted for power and this promises potentially even greater efficiencies than the stellar mass ones (albeit, you would not be gaining a net power gain here, this is strictly for power storage and potentially gravity generation purposes).