I can't say I feel the same as Knicks - especially for most of the Tarja era albums. Yes, they started with a certain formula on Once that holds to this day (or, more precisely Endless Forms), but the albums before I find much more innovative and intriguing. You don't hear them doing something like Wanderlust, nowadays. And even then, the Anette-era to me was a pinnacle of this "formulaic" approach - what they did, they did great, still kept the regurgitation of ideas on an acceptable level + were experimental in ways that did not put me off (most of Imaginaerum, including Slow, Love, Slow etc.)
With Floor... they don't suck and I actually can enjoy EFMB (and I'm gonna have to give H:N another chance, one of these days), but it's either a repetition of the formula, now including more and more previous riffs and ideas and the rest gets lost in ambience and bloat. And Song of Myself was the furthest I was willing to go as far as Tuomas' self-indulgence is concerned and he ovedid that many times over just on the last two albums alone.
And, actually, Oceanborn might be my favourite, or at least really high in my ranking. Yes, Tarja as an opera singer is not as good as Floor as a "classically influenced" singer (meaning Tarja is just a good opera singer, Floor as a "non-opera" singer is fantastic), but without her, some of the magic and wonder was definitely lost.
But on the other hand - let's be realistic - they never were really musically complex or untrivial, in the way Epica often are.