Most accessible would be imo are TL, IPT, PHD, HDT. You can join all these trackers right now with a donation or buying a seedbox for one month to get an invite.
TL/IPT are general trackers, I would prefer TL over IPT personally, they have a good amount of HQ encodes, remuxes, WEB-DLs....but I also find them good for re-encodes / x265 encodes. Particularly when you don't need the best quality of some TV series and want to save space. Groups like QxR (ImE, Silence, Panda, Tigole, etc), TAoE, Vyndros, EDGE2020, YAWNiX, etc are pretty good for them here. TL also opens often for free signups, they probably will like 2 more times this year, usually around holidays.
PHD/HDT I would consider more "HQ/HD trackers" they have restrictions not allowing some uploads, i.e trackers like these will usually ban those x265 groups I mentioned before deeming too low quality. But they have lots of remuxes, web-dls, and HQ encodes. PHD in particular usually is very fast with pre-times on latest p2p releases from groups like NTb, TEPES, FLUX, LAZY, KiNGS, etc as they upload. They also have a lot of remuxes from EPSiLON and their current remux group TRiTON.
I can't comment much on IPT or HDT, but know they are similar to TL and PHD respectively.
The downside of these trackers, generally, they're dead ends to getting into other trackers. They don't have invite forums. PHD has a way to access the AvistaZ sister sites....trackers to get into other trackers becomes a whole different can of worms.
Personally, I've moved onto different trackers for the most part...but do still occasionally use PHD and TL. Sometimes PHD is faster to upload things. Sometimes, just by the sheer size, TL has more stuff. I would have said look into /r/opensignups for when trackers open up...but on the fediverse I don't know a comparable place.
Since you just say 'best content' I'll stick with general trackers. TorrentLeech is quite good and somewhat regularly holds open signups. IPTorrents is another big one that you can just donate to for an invite. FileList is another, but isn't quite as easy to get into.
Unfortunately, "most accessible" and "best content" are often att odds with each other. IPT is accessible to anyone with $20, but is despised by the greater pt community. TL is easily accessible but if you're looking for something older or somewhat obscure you'll come up empty most of the time. They are probably the best option for somebody who is not in any private trackers, though.
If you are getting started in private trackers, you will find out that it gets easier as time goes on, but at the beginning it's a bitch. Back in the good old days of reddit, there was a sub called OpenSignups. It seems to be dead now, but, try this, it seems to be getting started:
there are some pretty good guides on how to get started with private trackers out there. the easiest route, imo, is just like it was before wcd was shut down. wcd was basically open, as long as you took your time with the interview process. once in, you follow their simple rules and you easily got access to the invite forum. from there, the private tracker world opened up for you.
same goes today, except what has been replaced with another music tracker that operates pretty much the same way.
Aside from TL, which has tons of content but is all over the place quality-wise, you can consider aither. They shouldn't be too hard to join, have all your mainstream content, and have recently pivoted to focus on quality of content. Basically the other side of the spectrum from TL.