You asked the right question, and no, the data presented isn't causative.

More than half of people who died in England last year were on an NHS waiting list, according to statistics.

Unsurprisingly, old people are often on waiting lists for things like knee and hip replacements, and these can be long. They sometimes die while on these waiting lists. In total, around 600,000 people die each year in the U.K. It would be unbelievable if half of those people died because they didn't receive medical care in time.

The article has merit, but the headline is total clickbait.