But that's the point, it doesn't depend on a "neutral" speed index, it varies from website to website, ISP to ISP.
If you're in Jakarta trying to access a certain website, if that website is available at the local CDN might make a bigger difference than which ISP or even which plan you're using.
You could have a 1Gbps fiber connection from your ISP in Jakarta. If you're trying to access a website in Singapore the your ISP's international link is congested, that 1Gbps will be useless.
OTOH, if you have a 10Mbps connection, and you're trying to access a website replicated at an Akamai CDN in your ISP's network, it will be way faster.