Polyamory is inherently shallower than monogamy
Don't get me wrong, there are "monogamous" people who feel entitled to a romantic relationship, and are thus unappreciative of their partner, do not genuinely want a monogamous bond with them, and care more to use their partner as an object of desire and means of following "the life script" rather than a life partner. People who prevent their partner from having friends, from bettering themselves, from having a career or hobbies. As someone who was formerly involved in these spaces, poly people often come from these broken monogamous relationships that lacked genuine reciprocity and love. And I feel for those people.
And, hell, I believe people should be able to live the lives they want as long as they don't hurt anyone in the process. A bit like certain kinks, what you do in your bedroom with your partners and only those others who have consented, that is none of my business. But these people will also claim that they have a greater capacity for love, that they "have so much love to give," that their love is "limitless." There are books full of opinionated bullshit dressed up as "the truth they never told you" (looking at you, Sex at Dawn). But it's genuinely the biggest lie they tell.
The argument that you can love more than one partner because you can love more than one child? Children are dependent on you for survival. They do not choose you nor do you choose them. This is a fundamentally different stakes than that of a romantic partnership. And the thing is... a child who has zero siblings does report feeling greater closeness to their parents than children with siblings. Because, who'dve thought... turns out! humans, especially young ones, struggle to feel closeness when they are rivaled for your time and attention!
The argument that monogamy is a post-agricultural invention? It's literally, once again, fucking projection. Even though they were often tolerant of the lifestyle, our nomadic hunter-gatherer ancestors actually were monogamous at higher rates than modern Western civilization. The age of agriculture brought about the legitimization of the accumulation of wealth and social disparity, you know, the exact criteria that exists in promiscuous animals? Don't even get me started on the "naturalness" argument...
When you have only one partner (whom you actually, deeply love), and they only have you, you are forging a bond with them that is not only words and emotion. Because even if love is limitless, time is very much not. And, ultimately, love is more than an emotion. It's your actions, your mindset. You can indeed say that you "love" 5 individuals equally, but is that really the truth, when you spend only 20% of your romantic energy on them? Instead of giving them your love and affection every evening, you give it once or twice a week, or maybe you give your divided "attention" while you're texting your others, or maybe you set specific day limits for each. Really, genuinely, it isn't about needing an outlet for "all your love." It's a fucking excuse to seek novelty using human emotions and bodies, and calling it freedom (to fuck around, to think about others guilt-free, to avoid getting "too close"). It's genuinely a preference for variety.
Monogamy, however, is concerning the depth that you go together. The closeness of attachment. The density of experiences you have together. Through monogamy, I get(!) to come home to my wife every day. To dedicate certain days to helping her during the weeks that she's strung thin, and vice versa. To think about her when I think of love. To spend time thinking about dates to take her on, new ways to impress her. If I'm going to cut that time in half, into thirds, into fourths... it's not really romantic love. At least, not devoted love. Not deep love.
Their claim of "limitless love" makes zero sense, mathematically, neurologically. They are either manipulating others, or lying to themselves, when they say this. Genuinely, I would have no problem with our differences if they would not pretend that what they are practicing is a "greater" love or a more evolved love. For polyamory to work, you literally either need to be traumatized, have certain genetic mutations, or you need to put yourself through extensive self-gaslighting and suppression to "correct" your urge to feel jealousy.
Again, people should live how they want to live. That's not my issue. Just wish they would stop making these claims that what they have is "more love" when it is merely a tradeoff for less "love-density" per partner for more variety.