It's because Orchid and Morningrise define a style of writing music that Opeth have long abandoned and in essence, have really abandoned what they started out as being.
I'm only going to speak on behalf of Orchid here, because I'm not a very big morningrise fan.. I just think its another Orchid without the reverb and way more droning and boring guitar parts.
The reason I like Orchid so much is because of this 'riff patching' you speak off. There is a feel of randomness yet it all fits... I don't really know what's to say to make it random... maybe the fact that they dont always have a 3-chord run or whatnot to lead into the next song section? Or maybe because they don't have a solid droning rhythm and more standard song structures as the later albums to link it all up? What it comes down to for me is... that the later albums, being essentially all Rhythm/Lead aren't as unique as Orchid, and of course they are going to flow more coherently as the song structures are so predictable for the most part... I think Mikael is forced to write 'off the wall' riffs, as he puts it to make the music sound 'unpredictable', which I might add is the main goal of the band.
Orchid embodies 'unpredictable' and the essence of what the band started out as being... the ideas are all of course very simple, everything included, solos and all... yet its very raw and I can almost feel the years of work and emotion in that album... there isn't fancy production and a shitload of overdubs, yet it still holds up just as well or even better to the other material to some fans... just chance you say?
I can see why Opeth evolved the way they did, as writing material like Orchid and Morningrise would undoubtedly become redundant after a while, and obvoiusly they needed to try something new... yet it seems with every new release their songs become more standard in structure, so you constantly have fans praising them for making their songs 'flow' better. Well then I ask, how well will the songs flow when Opeth decide to only start using 3 chords in them?
The early albums aren't for everyone, understood, yet I think 'outgrowing' them in no way entitles anybody to feel like they have moved onto 'superior' things... they are merely different styles. If you preffer more standard style music... and I've noticed you like alot of Doom metal Changso... which from what I've heard like to keep the one idea going for about 10 minutes, so it makes sense that you would like the more straightforward material.