The changes they have made over the years have made it quite a different game from what you remember if you were a player from the old days who hasn't been back. Here's something I wrote a few years ago when EverQuest came up (with minor edits to fix some mistakes I just noticed and the addition of a big thing I left out):

EverQuest today is worth a look if (1) you used to play and want some nostalgia, or (2) you never played but would like to see what one of the classic MMORPGs was about, or (3) if you would like an interesting game, good for grouping or solo play, that has a massive amount of content even if you are playing free.

There were several big changes on the "live" servers (which are distinct from the "progression" servers, which I will describe later) that made the game a lot more friendly for casual and solo play.

First, a few years ago they added in-game NPC mercenaries that you could hire (one mercenary at a time per character). You can hire a tank, healer, melee damage dealer, or ranged damage dealer, and the AI for the mercenaries is pretty good. They "understand" group play.

With mercenaries, a whole lot of formerly full group only content can be taken reasonably by a couple players each with a mercenary, and even a lot of it can be done with one player with a mercenary at least up to level 60ish if you are playing free and up to at least mid 90s if you are paying [1].

Second, they introduced a new line of armor and weapons, Defiant Armor and Defiant Weapons. These things drop from a lot of normal encounters, but the stats on this stuff is comparable to top raid gear from a few expansions earlier. With Defiant, you don't have to dedicate your life to equipping your character to be able to handle the top content from an older expansion. It's only the people who are chasing the leading edge that have to make EverQuest a second career, unlike the old days.

Third, on the role playing server, Firiona Vie (FV), there is a big experience bonus and very very items are marked NO DROP. So if you do need gear better than Defiant gear, you can trade for it or buy it from other players. Mana and healing rates are also higher than older players will remember.

Play on FV if you don't have some specific reason to play elsewhere.

Fourth, there are some new great quests. You start out with a book called the Tome of the Heroes Journey in your inventory. When you open it, it tells you several zones that would be good at your level. If you open when you are in one of those zones, it suggest several NPCs who have task, quests, and problems you might help with. Just following the Heroes Journey will give you plenty of fun stuff to do, and that is only the tip of the iceberg.

Fifth, there is a tutorial zone that you'll start in unless you elect to skip it. The tutorial zone has a series of quests that will take you through all the basics of the game, and get you to level 10 and decently equipped.

Sixth, if you have access to an old account, there is also a thing called "Veteran Rewards". For each year of your account, you get certain bonuses. One big one, which will almost certainly be on your old account, is a free resurrection. Once a week real time, you can go to an NPC healer in certain zones and ask them for a resurrection, and they will summon all your corpses and then give you a 100% XP resurrection.

Other Veteran Rewards include a 15 minute resist, stats, and run speed boost, usable once every 20 hours, a health/mana/endurance complete restoration usable every 3 days, 30 minutes of double XP usable once every 20 hours, one that summons a banker to your location and one that summons a merchant (both usable every 20 hours), and a few more.

With a mercenary and a free account on FV, you've got an excellent solo game for a long time. Even better for a group of friends.

For those who played before, and are nostalgic for the old days, they have "progression" servers. There are several, but the overall theme is the same. A progression server starts with some old version of EQ, and then progresses through the expansions. Progression servers do not have mercenaries, or Defiant armor. Heck, they are even missing later UI features when they start, such as the wonderful multiple target tracking system that the live servers have.

Progression servers have other rules, varying depending on server, to try to recreate the classic EQ experience that server's players want. For example, one of them is a "true box" server. That means you can only play one account per computer at a time. If you are one of those people who wants to play N characters at once on the same server, you have to have N physical computers if you are on a true box server. (To be clear, you can have more than one character on a "true box" server without having more than one computer. You just can't have more than one character logged in on the same server at the same time unless they on different computers).

They also differ in when expansions become available. Some do it on a fixed time schedule. Some do it when the endgame content of the previous expansion is defeated. Some do it by vote. They also differ in how far they go. For example, Agnarr unlocks expansions on a schedule, but will stop at Planes of Power plus the two smaller expansions that followed that. Many consider that the best era of EQ, and Agnarr will be frozen in that era.

Progression servers are not available to free players.

So for those who want a shot of nostalgia, or who never played and want to check out the classic game, the best thing to do is watch for the next progression server launch, and subscribe. A new progression server is always a high population server, with population density comparable to the old days.

System requirements are quite modest by today's standards. My ancient PC (Asus P5Q, Core 2 Duo e8400, 8 GB RAM, Nvidia GeForce GTX 460) has no trouble running two instances of EQ at once. It could probably do 3.

[1] The difference is mercenaries. There are apprentice mercenaries, with 5 skill levels (tier I to tier V) and journeymen mercenaries (tier I to V). Free players can only hire apprentices. Around mid 50s a tier V apprentice starts to struggle.