To critique a bit when establishing your lighting base go big and then back things down to something that’s a bit more reasonable and trust your eyes are telling you the truth. By default most applications will be set to a default that’s not even close to what it should be to produce the kind of result your looking for.
If it takes a 1024X light map to get the job done then that’s what it takes.
Using the default materiel is not going to work well as UE4 uses physics based materials and lighting that works in tandem with on another. A light trace is projected from the point source that when it strikes a material surface tells the light compiler how light needs to bounce off the surface based on it’s properties. Light bounces off a metallic or plastic surface a lot more than it should off a mat surface so if you make all your walls metal light should bounce like crazy.
With out a material to process you land up with what you got where light goes splat and there is no real bounce/renderosity effect occurring.
Last observation you have way to many lights and trying to flood an area based on the assumption that they are actually real lights and like baking a cake you need a few more ingredients
First observation lights are not all white but contains a mix of diffused colors based on the kind of light it is. Add a touch of tint like a yellow or orange, and as in a little is a lot, you will get a softer light that does not look monochromatic. Next you will need light(s) to act as a fill to paint the canvas so to speak by turning off inverse shadowing of a single light with enough of a level to see but yet still difused. From there you have your base lighting that you can added or remove point sources as you build up the environment.
The standard lighting setup used is called Three point lighting.
Rule of thumb in a physics based edit environment is less is better and with the right mix of helpers and materials you should get a much better result by trying to force lighting using 6 point sources in a given area that does not serve any other purpose.