Well, on one side we have zero examples of open engines actually working well, on other we have long nuanced history of SEO vs search engine fighting unending battle, with SEO side trying to circumvent every way the search engine is trying to stop them from poisoning the search results. And barely edging out on that.
Being idealistic about it won't change the outcome.
Altavista was initially a demo of the capabilities of DEC Alpha CPUs. It was initially amazing. It got taken over by SEO rubbish, and beaten by Google who invented PageRank to get good results again.
PageRank was initially much less prone to SEO shenanigans because it relied on signals from other sites (incoming links) to decide how important a result was. Of course, as Google became more popular, people started sharing links on other pages and so on to cheat the PageRank algorithm. And Google have been caught in a fight with SEO ever since.
Being idealistic about it won't change the outcome.