Is my toilet waste line too long w/ too many fittings?

My relatively new home has had toilet flushing problems. Other than the tight bend in the toilet P trap, the outlet has the following fittings:
Toilet outlet 90 el, a horizontal 45, about 8" straight, two 90 els in vertical plane with a vent connection off the uppermost 90, then another 45, and about three feet horizontal run to a wye into the 4" waste header. The fittings and plastic line are 3". Is this connection contributing to flushing problems? Are there too many fittings and straight sections?

pipes

No. But I hope you mean the "S" trap inside the toilet itself when you refer to the toilet's "P" trap.

I would be thinking that the problem is the toilet.

Change that to something decent, and your problems may be over.

My son just replaced a customer's Mansfield toilet, the lady of the home was wearing rubber boots and trying to plunge it clear.
He took care of that and replaced it with a Toto Ultramax.
Things should be much better for her now.