LDP gave us BGP-free cores. Don't underestimate how much that changed the game in large networks. BGP converged faster and core routers didn't need to do anywhere near as much. SR is a better way to do that now and LDP/IGP sync was a huge pain, but IMO BGP-free cores changed the SP game as much as route reflectors did.

LDP also enabled L2VPN and was an IGP-bound mechanism to enable MPLS VPN, which was always the killer app for MPLS.

LDP by itself? Meh. But it opened up a whole lot of other possibilities.

What are all these acronyms? I read the first paragraph but it really doesn't give much context if you're an outsider.

im my opinion, segment routing is more complex then a proper RSVP implementation.

running a PCE also adds a massive failure domain compared to the decentralised nature of RSVP.

Does RSVP have a million bells and whistles? yes. Segment routing also has a billion different bells and whistles, and those are far less mature.

We have just performed basic delay performance comparison with MPLS, SR-MPLS, and SRv6 in a small network case study with Cisco Modeling Lab (CML) and the initial results are very promising. SRv6 has about 48% improvement over original MPLS and 10% improvement over SR-MPLS. This delay improvement mainly due to the lack of LDP in Segment Routing approach. Perhaps later we can check other performance metrics as well and without LDP the node processing overheads will also be much better as well compared to the original MPLS. Scaling to the size of the global internet should further increase the improvement margins even more.