+1
If you write a lump of text that even you, as the author, label an "infodump," mark it for serious revisions on the next draft.
Keep in mind that LOTR was written in a specific elder-day style for a very specific reason, and it was also written many, many years ago for a different audience than exists now. Using Tolkien to justify infodumps doesn't fly unless you're time-traveling back to when he was fresh... or unless you're intentionally writing for a niche sub-market of epic fantasy. You can indeed write fantasy, even epic fantasy, without resorting to Tolkienian infodumps. As has been mentioned, there are many non-dumpy ways to convey backstory, some of which serve double-duty, such as revealing character when, for instance, one character sees the ancient city as a beacon of civilization while another sees it as a cesspit of corruption draining the life from the land. And when you must resort to telling, do your best to keep it to small bites - and do try to avoid the stale old chestnut of having a character attend a lecture with Professor Infodump droning on for a chapter.
One important thing to remember is that authors, particularly new authors, often overestimate the amount of backstory that a reader needs to specifically be told. If I may use a construction metaphor, the worldbuilding from which infodumps stem is like the framework and foundation of your story-house. You, as the author, ought to know as much as possible about the world so you can build it consistently, but the audience shouldn't need you to tear off the drywall and rip up the carpets and force them to peer into the crawlspace with a flashlight to reveal that, yes, you did indeed use proper framing and include good wiring. They'll pick up on it when they see the walls are straight and the lights come on and the stairs don't collapse when they try to go up to the balcony.