If you're going to play Ultima Online in the modern day, I would strongly recommend setting up your own server for just the bros. I would recommend using the open source classic client. It has some jank (mostly visual) but improves quality of life with things like zoom and large container images. You can see an example of some changes I've found enjoyable (for playing without a bot economy) by looking at our server.
I really like Ultima Online for a bunch of reasons but there are significant problems with the general user experience. I go out of my way to opt out of the bad and opt into the good. The root of all evil is the bot economy.
Slot inventories are for idiots.
No game has leaned as heavily or as seamlessly on thematic containers as Ultima Online. Organizing your every day carry items into pouches is zen. Decorating your house to have wardrobes, storage chests, mailboxes, and barrels is ridiculously satisfying and immersive. When you can "put an item on the table", "add it to the keyring", or "check in the bookshelf" -> without any additional menus or lag, the world becomes tangible.
Ultima Online uses a fairly unique system of skills rather than classes to determine the abilities of your character. It is unique in its balance of freedom and constraint. Many games, like The Elder Scrolls, have skills but no limits. Every character becomes a "do everything" character. There is no identity.
Ultima Online allows you to raise any of the 30+ skills to a value 0-100. Your total number of skillpoints cannot exceed 700. While it is normal to just choose 7 and call it a day, you can really have some interesting combinations. Metas will meta, but I'm quite happy with my 52.5 Magery build.
Items in Ultima Online (post Age of Shadows) use a randomized property system, similar to Diablo II. There are artifacts that drop from strong monsters with preset stats, but otherwise a lot of the game is farming critters for sick build-defining drops.
The combat of Ultima Online is fairly simple and reminiscent of any ARPG. It's the MMO and unique systems that layer ontop that make it something truly special. In an ARPG, every ability and mechanic is centered around combat efficiency.
In UO, we get a wider context from non-combat things like boats, houses, crate forts, taming animals, stealth, and treasure hunting. Combat becomes a thing that you do towards an end, rather than the end itself. I've played with dedicated interior decorators. I've been to in-game poetry slams. There's a popular sport called bagball. The world can be alive, if you live in it. That's just not true for ARPG#784.