There is a mitzvah to get up for a person aged over 70.
The link on the word “mitzvah” goes to Halchipedia. The first footnote relates to the age 70 and reads:
S”A YD 244:1 writes that it is a positive command to stand up for an elderly person of age 70. This is from the pasuk in the Torah (Vayikra 19:32) מפני שיבה תקום והדרת פני זקן. Kitzur S”A 144:2, Chaye Adam 69:2, and Aruch HaShulchan 244:1 agree. Birkei Yosef 244:4, however, quotes the Arizal who says that one should stand for a person of age 60. Sh”t Yabia Omer 3:13 and 9:13 writes that while the halacha follows S”A, one who is strict for the Arizal will be blessed.
We are grateful to Hashem that a larger proportion of the population is now over 70 years old than was the case over many years.
Has anyone commented on the nature of this mitzvah in these changed circumstances?
This excellent shiur by Rabbi Herschel Schachter explains that there are halochos where change in circumstances allow a change in the din (and halochos where they do not).