Fats, oils and grease are the worst offender. They go down as a warm liquid and set on the cold pipe wall, narrowing the bore a little more with every wash-up until nothing passes. Scrape and wipe pans into the bin instead.
Wet wipes do not break down in water, whatever the packaging claims. They snag on any rough edge in the pipe and then catch fat, hair and other debris — this is exactly how fatbergs form. The only three things that belong in a toilet are human waste, toilet paper and water.
Building materials are the quiet killer in renovation projects. Washing cement, plaster or tile adhesive residue down an outside gully sets hard inside the drain and usually needs jetting or descaling to remove.