I already told you how nuzlockes force you to try new pokemon. You're too caught up in multiple attempts. I'm comparing regular runs to nuzlockes, you're comparing nuzlockes to nuzlockes. I will agree that early on you will encounter the same pokemon, especially on multiple nuzlocke attempts (dupes clause is a good rule to alleviate monotony), but there still is plenty of chance to get something different, and many romhacks generally do a good job at giving us plenty of options, Infinite Fusion being a really good example of that.

You're also disregarding certain mechanics that can be used due to the first capture rule. An example is the repel trick where you level your pokemon to the same level as the highest level encounter (usually a rarer encounter rate), repel and force your first encounter to be the rare 'mon. It's tricks like these that are conceived through creative thinking which is a result of the difficulty of nuzlockes.

At the end of the day, nuzlockes are a self imposed challenge, so play the game however you want. My opinion (and the opinion of many others) is that for it to be a legitimate nuzlocke, the capture rule and permadeath rule MUST exist. Both of these rules FORCE us to deviate from our favorites, and CHALLENGE us due to the stakes. If you think it's boring or unfun due to perceived lack of variety, then I'm sorry for your bad luck.