Turn off barbarians, go Pangea, use different resource distribution. There are options other than changing the Eureka system.
The existence of partial buildarounds to mitigate the effects of a poorly-implemented mechanic doesn't resolve the problem with the mechanic. This solution is akin to advising people who disliked Civ V's implementation of 1UPT to reduce the number of civs on large maps.
Eurekas have the same problem as ideology in Civ V, and I've observed before that it appears to a common feature of Ed Beach designs that there's no subtlety to them - we see interesting ideas taken to an absurd and in some cases game-breaking extreme which warps the gameplay so heavily around them that, as others have noted, the game always ends up playing out much the same way.
Eurekas are too common, too restrictive in their requirements in many cases, too poorly-balanced, and probably above all too binary.
There are a great many eurekas that require reaching a threshold X (6 farms, 6 pop, 3 barbarians, 2 neighbourhoods, etc. etc.). Games like the Endless series are already capable of implementing scaleable achievements that track how many of X you've achieved - granted in those games as well you generally get a flat bonus once you've achieved X and nothing before that point, but there's no clear reason why that has to be the case.
Say your civ gets a small percentage boost towards a eureka every time it creates a farm (Fuedalism), kills a barbarian (Bronze Working), increases pop size (Political Philosophy) etc. up to a certain threshold - possibly the existing 50%. Then gameplay is less about min-maxing and more about calculating a trade-off between the value you gain for an incremental boost to a eureka in a particular game context and doing something else.
That also rebalances boosts from spies and Great People, as those could still give the full bonus - which makes them more desirable and gives you an alternative way to get specific eurekas that are less useful to rush through game actions on any given playthrough. Ideally, eurekas would be balanced so that it varies with context which route is most effective for most boosts.