I know they seem to have a reputation, my comments are based on my personal experiences only.
You can judge the growth rate for yourself. I stop feeding it a year or so ago hoping it would slow down.
No special growing conditions. It has always lived on my lower Heliamphora rack that gets no supplemental cooling or humidity.
Not a nep grower (I have two), so probably just a lot of luck.
To be fair, ALLNepenthes need good humidity and a significant temperature differential between day and night in order to perform well, not just this species. There is a lot of hearsay/mythology about this species that gets shared in discussion and for the most part it's baloney. (Except maybe the part about its slow growth, which is pretty accurate)
My plant does not get "UHL" climate conditions by a long shot - in fact, this summer daytime highs in the greenhouse have typically hovered around 85F for hours each day. However, night temps always drop to 60F or lower, often as low as 52F each night for much of the summer. That temperature differential is important for long-term health of the genus (notice I didn't say "species"?) But it's important to point out that my plants would not be happy at those temperatures if there was not good air movement, high humidity (always above 70%, even when its 85 in there) and shadecloth to reduce light intensity.
I've noted in the past that people sometimes fixate on one or two cultivation details (such as upper temperature limits) and ignore all the rest of the (equally important) facets of Nepenthes care, and that is likely to result in unsatisfactory results. It is important to make an effort to meet all of the cultivation requirements for the plants you care for, not just some of them. "Two out of three ain't bad" is a great lyric for a song, but it's not going to do much to advance your horticultural skill set.
I have a baby macro it pitchers like crazy even despite it shrinking cause my light broke. I just got my light today so hopefully the driving stops but since i moved it to a make shift shaded tank/tent area with a fogger running and mistings throughout the hotter days it seems to be growing a larger set of Leaf. I may have to switch out my HLs and UHL for intermediate and LLs which is gonna be a learning curve cause I'm so used to growing HLs and have very few LLs . etc.. SoOo if temps are gonna be anything like they are this year next year im gonna have a lot less HLs in my possession.
My macro is still a baby it grows relavently slow but it does pitcher like crazy despite all the craziness going on
In my experience, N. macrophylla starts out slow, but grow faster as it matures. I have grown mine in an unheated basement, in a terrarium, where the lights raise the temperature while on and it also naturally cools at night. I make sure the air movement is good and I use live LFS/cypress bark mulch net pots. I water with R/O and feed the pitchers. I use a mix of T5 cool white and LED lights.