SS is not overpowered. Compare truthfully with a +2 dex ASI !
+2 DEX ASI means +1 AC ! +1 DEX save ! +1 to hit with DEX ! +1 to damage with DEX = all ranged and all finesse! +1 to several DEX based skills!
And all of that is active all the time and in a multitude of situations.
SS cover ignore only applies if there is someone hiding behind partial cover, and it is not absurd a sniper takes someone out through an arrow slit sized opening, things like these are absolutely existing IRL.
But as said it is contextual, you need the "enemy takes cover"- situation
SS range ignore same. SS confirmed kills IRL are 1-2 miles away! But in game as before you need the appropriate situation .
SS -5/+10 does what it does. Again highly situational unless you do not roll the to hit? It works quite reliable against mobs up to AC 12. With advantage it works reliable up to AC15 or so. Beyond that it is better to leave it out, unless you got some +2 and up weapon or are of high level.
E.G: Hunter ranger, archerstyle, +1 bow, level 6 , DEX 16: Ok you got that +9 to hit, but with the -5 it is only +4. so take a mob with AC18. You need to roll a 14+ on a d20 (35% chance to hit) to hit. With the usual power build (hunters mark, colossus slayer), you want to make sure the mob gets hit in the first of your two attacks, so you can get your colossus slayer extra 1d8 (which requires the mob to be injured to be applied once per round) to kick in from round 1, so that is of course also a reason, why you also want your second attack in the first round to hit.
So if you botch it, not only you lose one or both attacks, but also 1d8 from colossus.
Same ranger but DEX 18. Same opponent. He got +10 to hit. Versus the AC 18 mob he only needs to roll an 8 or higher! Which is a 65% chance, so almost double the chance versus a heavy armored mob. Not only does he get his 1st round burst working in double the cases, especially if the DM (like he should) does not instantly communicate the mobs AC, but also his survivability is far better, because of the higher DEX stat,