sure, i had never disagree that catching up to existing tech is easier to innovating new tech.
but that's not at all the point here, you argued that china isn't catching up. yet reality shows otherwise.
also you are clearly trying to mislead by saying china had the j-10 since 1998.
i was using the in service dates
but if you want to use first flight, then the f-22 first flew in 1997, heck the yf-22 first flew in 1990, while the j-10 had no equivalent prototype and was testing its component tech using j-8 and j-7s, so if i wanted to mislead like you, i would had said the us had 5th gens 18 years before china flew a prototype 4th gen, a full 18 years the US had a 2 generation advantage vis-a-vis china
so no matter how you look at it the gap has narrowed significantly in 2022 even while the us is still currently ahead. i fully expect the us to come out with a 6th gen first but i highly doubt the gap will be 18 years.
and yes, not all planes are equal. the f-22 has powerful engines but its electronics are clearly old at this point, its missing sensor fusion and while there are plans, it still does not have irst. the f-35 is overweight and had to compromise for the VTOL version. the J-20 has the benefit of newer electronics while not having to compromise, other than for its weaker engines. its fully competitive with either the f-22 or the f-35, unlike say the j-8 vs f-22.