Castes are there though many have said since the time of the Buddha that they should be eliminated. Our Constitution has provision for dalits. It was similar to provisions in the Constitution for the downtrodden in other demoratic countries. Much later for crass political reason late V. P. Singh Mandalised the Constitution.
Muslims do it. Christians do it. That doesn't mean Hindus also should do it.
Denial of entry into temple for lower castes was made illegal long ago. Now there is no bar at least in celebrated temples like Guruvayoor. As for the entry of women in the menstruating age why not Sabarimal follow the same practice as other temples.
50 years ago only Shudras of Kerala were going to Sabarimala temple. They will wear black lungis and will have all that paraphernalia of those who take a vow to go to the Mala. They will go house to house like beggars offering their services to take offerings to Sabarimala. In due course through propaganda all kind of people from all the Southern States started crowding. In a Hindu temple the pujari is a man who just does a service. He does not have a higher status. In a Church the priest is a shepherd and the Chruch going are sheep. They go to the shepherd for advice and guidance. In due course the pujari at Sabarimala also started assuming upon himself the status of a shepherd. The crowding devotees will touch his feet and seek his blessings. There is a saying 'in a temple God may bless you, but the Pujari will not".
If there is anything called spiritual, Sabarimal is a spiritually deteriorated place. The Thantri there commands everything.