'95-ish? That's the first meeting I remember where there was a realistic attempt to propose something to NASA. I don't think there wasn't much research funding before that. Not that long a history.
Mostly the cost estimates have gone up, especially after the scrutiny brought by JWST overruns brought more honest costing. It was always going to be a flagship mission. We could debate whether eLISA is actually going to save that much money over the combined US/ESA LISA proposed in Astro2010, which we cast as the sweet spot of science per dollar.
And as far as eLISA and 2034, well, I ain't holding my breath for funding profiles that far in the future. Actuarially, it's unlikely that it'll fly in my lifetime (scientifically, and otherwise). So for me, not better than nothing.