Bhagavadgita never advocates caste system. True meaning.

Hinduism and its scriptures DOES NOT support the caste system as practiced today!
Bagavad Gita emphasizes the importance of Varnashra Dharma in verses 18:41-48. Varnashra Dharma is absolutely different from Caste system. It is called Varnashra Dharma, because it is great a Dharma which can be applied to every society!

Indian Government has categorized their public servants into Group A, B, C and D or in Class I to IV.
Class I or Group A-Executive power vested in these categorized public servants with decision making powers
Class II or Group B- Officers with limited supervisory or subordinate managerial role.
Class III or Group C- Semi skilled with no or lesser decision making authority
Class IV or Group D- Manual workers, Unskilled or semiskilled

In other words the govt. admits that all employees are not equal under any hierarchical system. It is true that each one of us has certain abilities and skills which may be different from others. It is true that not all of us have the managerial skills required to be a manager. Not all of us have decision making skills required to be in the top management. This class division is present in any society if you to care to look. In other words Varnashrama Dharma is present in all societies.

Varnashrama Dharma's, four divisions were created so that the power would not lie in one varna. The Bhrahmins had knowledge, the Shathryas had strength and war skills, the Vysya had money and the Sudras had the physical power. All four have to contribute to the successful running of the society. For example in a war situation, the Bhrahmins will contribute by way of knowledge and strategy, the Shatryas will actually execute the strategy, the Vysyas will contribute the money required for buying military ware, the Sudras will provide the man power. It was working fine as long as the Varnashrama Dharma was followed. In the Varnashrama Dharma it is possible to change ones Varnam. Sruti is categorical when it says that, all are born Sudras, but ascend up in the Varnashrama Dharma by his conduct, efforts and intelligence, again backed by his Karmic account. Similarly an offspring of a Brahmin can descend down. There is no hard and fast rule that one born in one varna will remain in the same, unlike in a caste system. Caste system DOES NOT have scriptural sanction, whereas Varnashra Dharma has. Varnahsra Dharma is the most scientific human management system. Caste system is the cruelest human oppressive system! In the true Varnashra Dharma one can change one's Varnam by his education, behavior, accomplishments and usefulness to the society; But in the caste system it is not possible, which is a man mad distortion of the Varnashra Dharma- 1000 years of foreign rule and human selfishness and a tendency to exploit are the main reasons for it. Smriti is very clear when it says: जन्मना जायते शुद: कर्मणा जायते द्दिज:
वेदाध्यायी भवेद्दिप्रो ब्रहा जानाति ब्राहाणा:
'Janmanaa, jayate shudrah
Karmana jayate dvijah
Vedadhyayi bhavedvipro
Brahma janati brahmanah'
– By birth all are born as dull (sudra), and only by nobility of action is born the smart (dvijah). By studing Veda he becomes learned (viprah), and only when one realizes Brahman, does he become a Brahmana. It is not Hinduism's fault that we have 4000 and odd castes in India and we are required to fill the caste columns. It was the British who institutionalized caste system into the government machinery.