A TA works for you; a travel consultant for a cruise line works for the cruise line.
The cruise lines definitely want to keep TAs in business. If they did not, they would reduce or eliminate the commissions paid like the airlines have done.
One hint, call TAs for quotes rather than go by what is listed on their websites. Often they are not allowed to post their discounted prices. As an example, we once found 3 cruises on our TA's website that met our time frame and itinerary needs for an Alaskan cruise. The Princess ship we ended up sailing on was listed as the most expensive, but ended up after he discounted it, the least expensive.