How good is 800 elo player

Knowing multiple openings might not be useful, but it makes the game more fun. I only know a few (italian game, sicilian def, slav def, french def, queen's gambit, ruy lopez) but knowing many prevents me from replaying the same sequences of moves over n over. I used to play ONLY the Italian game, and it got boring. Sure, knowing the first moves of the game might increase my rating, BUT ITS BORING TO PLAY THE SAME OPENING OVER AND OVER.

-not useful for low rated players, that is

Uhh... Why have you learned them? You haven't even passed 1000 yet. I mean there's nothing bad about it but it's no use at that point.

It makes the game more interesting.

Occasionally I play soldiers OTB. They do not study the game at all. They just enjoy an infrequent thinking challenge. In their profession basic tactics and situational awareness are very important. They would beat the 800 here, and give me a lot of challenge. 

Hello, hello Infantry! Queen of battle follow me!

800 elo is quite a respectable player, not fancy but a basic no nonsense model who gets the job done

The average player on this site is below average. 800 is below that.

Nothing wrong with a beginner. Everyone starts there. Those who recognize that’s where they are are less likely to stay there.

I started at 800 with my first game on chess.com, then got killed pretty frequently until I dropped to around 550. Now I've clawed my way back up to a little over 800 and I've improved a ton but still do miscalculations sometimes with the occasional dumb move here and there. People on chess.com as a whole I've found are pretty strong for their rating no matter what it is, if that makes any sense.

The worldwide average player doesn't even bother to play online. Therefore, the average player on this site must certainly be stronger than said player. Moreover, 800 is above the average for this site as a matter of measurable fact.

I've playt ches finfty tune yearts n I'll say getnthur and get it boiy yeeee yeee

The site’s average rating is now 634. It has been steadily declining the past few years. Was a time when it was near 1100. With such a large influx of complete beginners joining the site, any assumption that online players must be stronger on average than those who do not play online must be regarded as extremely dubious.

Despite such averages, players below 1200 still show by their play that they are beginners.

Eric Rosen’s speed run does a good job of highlighting how beginners near the 800 level play.

Sometimes, even a 1600 will make the sorts of fundamental errors that the 800 made in Rosen’s video.

When I was coming back to chess after more than a decade of minimal play, I thought I had a good grasp of checkmate patterns. My OTB rating was in the 1400s. I was mildly dismissive of the advice of a strong player that I should get Renaud and Kahn, The Art of the Checkmate. Nonetheless, I did get the book a year or two later. I quickly discovered that there was still a great deal that I could learn about checkmate patterns.

I recommend that you (everone) get at least one of these books.

White to move

It is not a mistake. The site only allows one response. Either move should be acceptable, but that is not supported. If you made it that far, you’ll get the entered solution on the second try.

800 elo players are below average and pretty bad, missing a lot of checks and other things

800 ELO players are objectively well-above average according to the site's own percentile readout of the global average curve.

An 800 on Chess.com is dfiferent than an 800 on f.ex gameknot correspondence chess. On this site an 800 is definitely intermediate, knowing quite a lot about amateur chess.

They know general opening principles (develop, develop, develop), general endgame technique (Lucena and Philidor), and they love tactical blows and fast checkmates. (forks, pins, discovered attacks, Anastasias mate, etc,etc)