I played it for the first time a couple years ago. Was a JRPG console-only player for most of my life, but about 5 years ago started diving into the cRPG well.
1) First thing is that, as others have said, Exult is a must. It lets you put a background against the text, which makes it actually legible, and smooths the painfully jerky scrolling. I honestly would not have been able to play the game without those quality of life improvements.
2) The writing is incredible. Every NPC has a meaningful story. Every town is chock full of pathos, humor, grand tragedy and the rich texture of everyday life. From a modern point of view, this is the aspect of the game that holds up the best. Indeed, the writing stands head and tail over modern open-world RPGs (excepting Witcher 3 but that's more a linear story that is set in an open world).
3) The game is fascinating in that it goes all-in on a simulationist approach that has been all but abandoned by modern RPGs. Detailed NPC schedules where they work, eat, and sleep, tons of possible interactions in the world, lack of visible stats associated with weapons and armor, an inventory that mimics sorting through an actual backpack, and so on. It's sophistication in this regard is matched now only by immersive sims, and those work at a much smaller scale than what Ultima 7 attempted.
4) The game also makes clear why modern "mainstream" games have abandoned that simulationist approach. The core problem is that a lot of the simulationist aspects just aren't much fun. For instance, your backpack has a "space limit" where you can only have so much volume stuffed into it. Realistic, in some sense, but the volume occupied by any given object is not communicated, leading to a huge amount of trial-and-error just trying to get everything into your party's inventory. Even worse, it's super easy for a key item to literally get buried in the bottom of your pack and it will be incredibly annoying.
Not only is this not fun, it's also not really realistic. If you were "really" in the game world, you could just see the volume of an item and when your backpack was full. If you needed to find something at the bottom of your pack you could just empty your pack on the ground all at once rather than dragging out one item at a time. You would know how to evaluate the quality of a weapon!!!! So the simulationist aspect really takes away information and capabilities that you realistically should have.
5) Exploring the world is fun, but gets tedious as it certainly will not inspire the sense of awe today as it would have in 1995. Find the magic carpet ASAP (use a guide if you have to) to minimize frustration.
6) Combat is... well it's just there. Look up the location of the most powerful spells and stock up on the necessary ingredients so you can blast through it as fast as possible. Exult also enables mid-battle pausing which makes spellcasting in combat much easier.
7) Don't be afraid to consult a guide if you're stuck. The game can be infuriatingly obtuse. It's very easy to miss a crucial clue and have no indication of why you can't progress the main storyline.
I guess this sounds pretty negative, but I really enjoyed playing the game.
