Having a look at your rate of descent on final is a secondary way of assessing your profile, i.e 5 times ground speed equals 3deg or 5% profile
A Cessna 172 is not an airliner and should not be flown like one, although there are flying schools that treat the 172 as an airline type aircraft. With nil wind and 60-65 knot approach speed at around 1200 to 1500 rpm powered approach with full flap, the angle of approach in a 172 or similar light training aircraft is more like 5-6 degrees - not three degrees as on a typical ILS or PAPI angle.
The C172 is certified to approach power on or power off (idle RPM) for the same approach speed published in the manufacturers POH. A powered off approach (meaning glide approach) with full flap, is around seven degrees slope. To teach a stable three degree approach in the 172 with full flap and 60 knots requires around 2000 RPM which is equivalent to low cruise power and plainly inappropriate.