I think the issue is much less about whether the foetus looks like a person, and more about when the foetus is viable (as in, can live independently of the mother).

A foetus 5 minutes before delivery is clearly a viable human being that would be able to live independently of the mother. It's not a "clump of cells" any more than you or I. Delivering the baby also comes at no or extremely minimal extra cost to the mother.

A foetus at the point of conception is clearly not a viable human being, and given that it is literally comprised of two cells, can barely even be described as a "clump." Forcing a woman to carry this foetus to term means a 9-month hijack of her life, career, and health.

Somewhere between these two extremes is the point where elective abortion should be legal. Roe vs Wade placed this point at three months. Which is still weeks before viability, but gives the woman time to discover she's pregnant and make a decision about what to do.