Yes, a waste of time if you are doing it just to improve your employment prospects, unless you want to be an academic and have a realistic chance at that.
Is your PhD competitively fully funded because you are really good at your subject? Are you also really really committed to academic work?-- If so, you have a reasonable chance. If not, but you are on a studentship deal involving some teaching, perhaps with fees paid, you have some chance, but not much. Otherwise, no real prospects.
Look at the numbers: how few jobs, how many PhDs?
Outside academia, PhD does not really directly help with employment.
But, but , there are other reasons to do a PhD. It might help indirectly with employment, via the self- and time-management skills you pick up ... or the networking opportunities ... or, well, other things too, easy enough to see.
Or you might want to do it for other reasons entirely. Development of yourself as a thinking, rounded person; interest in the subject matter; curiosity; adding to the sum of human knowledge and understanding; avoidance of wage-slavery for a few years; meeting and learning from clever and interesting people; cocking a snook at contemporary money-hungry societal mores; a sense of achievement ... etc., etc.
My own reason? I got interested in a puzzle, tangentially connected to the subject of my first degree, found there was no extant solution no-one knew the answer! and started working on it myself (part-time of course; I am no Andrew Wiles, no-one was going to pay me). Some years later, with much assistance from some really clever people and following various part-time degrees in different places around the world I signed on for a PhD, finally solved the puzzle to my own satisfaction, wrote the thesis, published a few papers on it, wrote the book. (I would like to say, '...retired on the royalties', but no, this is very much a niche topic; your local university library probably has a copy, though very likely unread. It made me a little money, but you need to be super good to live off academic royalties and I am certainly not that.)
Doing a PhD was maybe not the best thing I ever did: that was having my children and enjoying family life. It definitely gets into the top ten, though (along with ... no I really mustn't!)
So, for me, definitely not a waste of time. But, you will realise, this was mainly through good luck.