It seems inevitable that those who play like there is an endgame end up grinding.
I think this mis-understands the game. It certainly doesn't sound like much fun, judging from the forum posts.
Some games rely on enticing end-game content to keep the player grinding.
Some games rely on deep or simply well designed game mechanics that are enough in an of themselves without the need to reward players.
Succesful games tend to rely a bit on both, but you can make an engaging game focusing mainly on one or the other.
Alas Elite Dangerous leans very heavily towards the first category, because it can't be the second category considering how shallow the game mechanics are.
Mining? Head for the closest RES, move 50km out from the beacon, then shoot asteroids along their axis of rotation, pick up the bits that come out using collector drones, fiddle with the refinery, rinse and repeat. If you feel really, really bored use prospector limpets to try and be picky, though you'll probably waste more time doing that than you would bulk-mining. You will see the entirety of the gameplay associated with mining in the first 5 minutes, and there is absolutely no skill or thought process involved. The most demanding task will probably be to look for a pristine metallic planetary ring within inhabited space on google.
Trading? Considering the economy is virtually entirely NPC driven and there are arguably no long-term trends in the evolution of price and supply (unlike, say, EVE), just find a high-sec high pop high-tech system not too far from a high sec high pop refinery system, ferry stuff back and forth
ad vitam æternam. And forget about 75% of the in-game commodities: they're not worth trading. You'll of course see the extent of what trading has to offer from a gameplay perspective in the first 10 minutes of doing it: access the commodity market, buy stuff. Fly to other station, access the commodity market, sell stuff. Now compare that to EVE where the economy is complex enough to let you engage in long term speculation based on the evolving politics of the universe...
Smuggling: Trading but a bit more tedious when picking a route and more involved in that you have to fly faster and have tighter control over your ship to enter the dock without crashing. Being scanned isn't really a threat though since the game only spawns NPCs (including the police) at predefined locations after you've entered the instance, way too far out to be able to scan you in time, instead of randomly (or why not, procedurally, yay persistent NPCs) setting their location to add some spice and difficulty. Of course all this extra involvement is balanced out by lower rewards (please don't mention the powerplay bonuses, smuggling shouldn't be limited to a couple spots where powerplay bonuses make things profitable), because in Elite Dangerous fun is a currency and you have to pay for it. Then again, just like trading, you'll see the extent of what it has to offer in a matter of minutes. You'd expect the concept of dealing with the underworld to be a bit more involved than a mere "I want to sell illegal things" menu option.
Exploration: Mechanically speaking the dumbest of them all. Jump to system, press the ADS button for a few seconds, profit. For extra credits you can fly to the discovered bodies and keep the nose pointed at them long enough to complete a scan. Shoul take about 1 minute grand total. Once that's done, you can jump to another system and do it again. And again. And again. And again again, because the transaction server is having trouble registering your scans anyway. Again, don't expect any knock-on effect: nobody cares that you went there, no minor faction will expand into those systems if you're not doing it as part of a CG, and players have far better options for mining in pristine metallic rings in the civilized bubble anyway. Not that it would matter anyway since FD limited the purchase of exploration data to a 20ly bubble around stations. You will find some pretty sights on your journey out there though, but that in itself has no gameplay value. Where is the complex gameplay you'd associate with surveying stellar bodies?
Bounty hunting: Combat is of course the most fleshed out part of the game, so that's a positive. On the specific topic of bounty hunting though, you would expect something more to it than just farming RES. Luckily with 1.3 FD added a bit more to it, with targets now flying around in supercruise too. A step in the right direction. Hopefuly eventually we get some more bounty
tracking instead of just mindless combat. Bounty hunting should be more of a detective's job, going after a target's tracks, checking station traffic reports, doing some guesswork, and then only ending the chase with a glorious battle.
Piracy: Pick low sec system, interdict hauler, shoot hatch or launch limpets, scoop up all 20t of hydrogen fuel and run away while punny police vipers plink away at your shields. Takes 10 minutes, doesn't require much skill. The cargo NPCs carry doesn't seem to be linked to the local economy, so there's a lost opportunity for some depth. Just like smuggling, the fact you're selling to a black market isn't used to improve the gameplay either. Now PVP piracy at least adds, by its very nature, some flavour to an activity that is like the rest very shallow gameplay wise. By the way, the crime update was a joke and didn't add any sense of consequence to criminal actions. One day maybe the police response will become a thing and force us pirates to make a balanced choice between sticking to anarchy system or risking our hides for higher profit in 'high security' space.
Some people here advised the OP to try a bit of everything, but that's the issue. The entirety of the gameplay associated with each profession is immediatly available to the player, and you need no more than half an hour to see everything there is to see in each of them, with the exception of PVP combat maybe. A good game of the scale Elite wants to be should have deep and interwoven mechanics. Elite fails in this regard, so all that is left is grinding for the best money can buy while using your imagination to pretend you're enjoying it. All of this in a curated universe where your actions are utterly irrelevant except when the devs want you to feel otherwise through the deeply involved task of filling up a CG's progress bar.