I disagree on a number of levels.
For one this is untrue of reddit. Sure if all you did was browse the front page logged out or /r/all this was kind of true, but a lot of people subscribed to some subs unsubscribed to other subs so my front page might look nothing like yours. Likewise reddit had an algorithm that weighed which of your subscribed subreddits got the most front page real estate which would also change up your front page a bit.
There is a fear that fragmentation would be the death of lemmy/kbin when in fact fragmentation was present on reddit. /r/gaming was default but there were so many other game subreddits from /r/truegaming patientgamers games pcgaming various console subs retrogaming and I could go on. In fact the ability to find a smaller sub with better discussion and a different vibe is one of the reasons why reddit alternatives took so long to take off. If /r/shaving isnt cutting it then I can create my own new subreddit /r/wickededge to better service my needs.
Reddit was full of reposts, redundant subreddits, repeated news, and different cultures. Reddit did use to be a bit more unified in experience back in like 2010 but we've come a long way since then. I think killing off /r/reddit was the beginning of the end of the more unified reddit.
But that said I can click all and sort by hot and I suspect that a lot of the larger instances with similar philosophies are going to find similar content in a similar order because of how everything is networked. So we will still have a fairly unified all.
Finally I dont think that lemmy should try to follow the footsteps of reddit. I think that a series of smaller but lively communities is healthier for discussion and enjoyment than a huge mega one. Reddit's front pages got TOO big and the quality of discussion suffered while thousands of people would rush into the comments of a threat to make the same exact joke first(even if the thread was several hours old). It's why I unsubbed from a lot of the defaults. If you didnt get to a thread a minute after it posted then you may as well be writing your comment out and throwing it into the trash. If you do get there in time, enjoy unrelated comments trying to be noticed by replying to you along with 100 people saying the same reply without actually wanting to talk.
At its core this style of site is a universal comment section for links and a message board. I think we're already on track to become big enough for threads to not be ghost towns, while being small enough that you can actually get a word in edgewise and the good comment not be buried by a low effort bad joke.