my friend, yuo have bristle marks, that or you have a brush that isnt meant for use with solvents (i.e. nylon or some other synthetic bristle), what can happen if you use a synthetic brush with an oil based coating can make the bristles of the bruch fall out, fray or stick in the solution, if that's not the case then the bristles may be too stiff and making little furows in the urethane as it settles. the solution? foam applicator as far as your streaky appearance, that could be several things. firstly, all finishes that come in a satin are manufactured as a gloss, flattening agents are then added to the mix to make it that duller sheen. the solution? stir thouroughly. Stirred not shaken, opposite of james bond's preference. shaking can put bubbles in it as with anything with a pigment, sreaking can occur if the solid pigments in your coating float or settle, making some spots darker/lighter than other spots. the solution?? you guessed it, stir. the flattening agents settling coupled with the pigment settling can give you some odd effects as far as how it looks when it actually goes on, a good solid stir can fix alot of your problems, also, that foam applicator will make for a smooth finish. poly hsades isnt a bad product, nearly all of the molding in my house is coated with it, it just takes a little background info to make it look right

Use a light colored rug with some pattern and the cooffee table that is similar to the floor will be great.

Notes on the photos: 1st pic is original table after cleaned thoroughly with scotchbrite. Round shadows are from chandelier. 2nd & 3rd pics are current state of table 😔

I'll get into what you should do next time after we talk about what you can do about this project. Without an unreasonable amount of work,you can't accomplish your goal on these. I reccomend going for old and worn look for the project or paint the legs and natural top for a farmhouse look. To prevent uneven stain on same legs next time,sand with 180 then 220 grit before applying preconditioner. Never wait overnight between preconditioner and stain. If the time window closes before you get stain on,just apply another coat of conditioner then proceed as usual. On the assumption you do alot of staining and want to strive for perfection,I'll explain the why so you recconize it in the future. End grain on ANY WOOD will ALWAYS absorb more stain than face grain. If you are staining oak,ash or other hardwood,conditioner isn't neccessar EXCEPT end grain.