I think varnashrama dharma was attested long before either of them or Adi Shankaracharya's time.
Varnas are already present in the Veda, through the MBh including Gita.
[In fact, Buddhism and Jainism did their usual trick (as what they did to Samskritam and a lot of other Hindu stuff): after screeching about the matter, they both tried to coopt varnas' invention as well, by coming up with backprojected stories about how a backprojected Buddha or mythical primordial Buddhist king or something came up with the yugas and varnas, and how a teerthankara established the varnas, respectively.]
Qs for you:
1. The fact that you highlight that Ramanujacharya and Sridhara Swami's writings both attest to varnashrama dharma,
is that because:
[a] you are surprised varnas still existed in their time? (even though varnas still exist somewhat today)
[b] you thought it did not yet exist in their time and were surprised to find it did?
[c] you have some other reason to bring the matter up? If so, what?
2. Also, why do you bring varna(ashrama) up in the "caste" thread?
Varnas are already present in the Veda, through the MBh including Gita.
[In fact, Buddhism and Jainism did their usual trick (as what they did to Samskritam and a lot of other Hindu stuff): after screeching about the matter, they both tried to coopt varnas' invention as well, by coming up with backprojected stories about how a backprojected Buddha or mythical primordial Buddhist king or something came up with the yugas and varnas, and how a teerthankara established the varnas, respectively.]
Qs for you:
1. The fact that you highlight that Ramanujacharya and Sridhara Swami's writings both attest to varnashrama dharma,
is that because:
[a] you are surprised varnas still existed in their time? (even though varnas still exist somewhat today)
[b] you thought it did not yet exist in their time and were surprised to find it did?
[c] you have some other reason to bring the matter up? If so, what?
2. Also, why do you bring varna(ashrama) up in the "caste" thread?
Death to traitors.

