So, digging into the background of the show itself
Because Amazon only bought the television rights to The Lord of the Rings and The Hobbit, the writers had to identify all of the references to the Second Age in those books and create a story that bridged those passages. These are primarily in the appendices of The Lord of the Rings, but also in certain chapters and songs.
Tolkien's estate was prepared to veto any changes from his established narrative, including anything that contradicted what Tolkien wrote in other works. The writers were free to add characters or details, and worked with the estate and Tolkien lore experts to ensure these were still "Tolkienian". They referenced The Letters of J. R. R. Tolkien for additional context on the setting and characters. Simon Tolkien, a novelist and the grandson of J.R.R. Tolkien, consulted on the series and helped develop its story and character arcs. He is credited as a "series consultant"
Also, a disclaimer is featured in the series's end credits stating that some elements are "inspired by, though not contained in, the original source material.
Because the writers were mostly not able to adapt direct dialogue from Tolkien's Second Age stories, the writers attempted to repurpose Tolkien's dialogue that they did have access to while also taking inspiration from religious texts and poetry. They tailored the dialogue to different characters using dialects and poetic meters. Leith McPherson returned from the Hobbit films as dialect coach and noted that Tolkien's fictional languages evolve over time, so they are different for the Second Age compared to the Third. The series's Elves mostly speak Quenya, a language described as "Elvish Latin" that is often just used for spellcasting in the Third Age. Dwarvish and Orcish are also heard, along with English, Scottish, and Irish dialects. The biggest deviation made from Tolkien's works,
which was approved by the estate and lore experts, was to condense the Second Age from thousands of years to a short period of time. This avoided human characters frequently dying due to their relatively short lifespans, and allowed major characters from later in the timeline to be introduced earlier in the series. The showrunners considered using non-linear storytelling instead, but felt this would prevent the audience from emotionally investing in the series. They said many real-life historical dramas also condense events like this, and felt they were still respecting the "spirit and feeling" of Tolkien's writings.
So anything you feel that deviates from Tolkien you can blame the estate and not amazon