I don’t think Twitter is dead at all. In fact, it has over 100 million daily users. With so many people out there, it has to be worth it. Personally, I like Twitter marketing, and it’s been one of the major traffic sources for several of my websites.
However, I don’t think Twitter works for all niches. I’d advise you to check if your target audience is there before investing your time and money. If you find that it’s good for your niche, learn everything you can about 2019 marketing strategies and get to work.