I've taken this list and filtered out words that have other parts-of-speech according to wordpos. It went from 28,479 lines down to 23,799 lines. wordpos definitely isn't perfect, so it's likely that there are many words still in this list that have other part-of-speech values. Here's the code I used:
const fetch = require('node-fetch');
const WordPOS = require('wordpos');
const wordpos = new WordPOS();
(async function() {
let text = await fetch("https://raw.githubusercontent.com/taikuukaits/SimpleWordlists/master/Wordlist-Adjectives-All.txt").then(r => r.text());
let adjectives = text.replace(/\r/g, "").split("\n");
let adjectivesFiltered = [];
for(let adj of adjectives) {
if(!(await wordpos.isNoun(adj)) && !(await wordpos.isAdverb(adj)) && !(await wordpos.isVerb(adj))) {
adjectivesFiltered.push(adj);
}
}
require("fs").writeFileSync(__dirname+"/words-that-are-only-adjectives.txt", adjectivesFiltered.join("\n"));
console.log("done");
})();