You definitely want as much money as possible in the pot with your strong hands, so, I think you're still ok to have a SRP on the flop and be able to size your bets to get all-in on the river with your strongest holdings...also, there's less variance now... I think your bet-sizing on a street should be indicative of equity distribution on the next street...So, preflop bet sizings should be determined by the ~1700 representative flops, as opposed to flop bet-sizings which only need to be determined by the handful of turn possibilities (connect, didn't connect, small, over, A, paired, etc.)...just like on the river, bet sizing is determined by the distribution of equity at showdown... much easier to have the right sizings postflop for that reason (and why river equity is a piece of cake, since you always "know" the ranges)
Trying to bet preflop makes it impossible to have "optimal" sizings/distributions, but it'straightforward to define a flatting range, since, flatting is always just relative to the pot-odds and equity on that street, since you're not giving the aggressor a chance to respond.
Wouldn't this make it better to not only flat / fold preflop and exclude 3bets all-together?

Your first sentence answers your question. Also when we get someone to fold preflop and win the money uncontested (and unraked in raked games) it's a HUGE win.

But, in order to 3-bet strong hands and get money in the pot, a certain percentage of "weaker" hands need to be bluffed to continue... It's "big" to win fold equity with hands that have relatively low equity, but the hands you're forced to balance still have >=35% equity vs a 15% EP open (suited connectors, small pairs)... Can't you get the same fold equity postflop with hands that have less equity vs range while balancing them with hands that have greater equity vs range than you would preflop? Dominating hands are getting ~70% equity preflop, but, on the flop, there're far more combos with >70% equity vs range, and they can be balanced with combos that have <30% equity vs range, rather than having a lot of hands in the 60%s and 40%s to balance each other out...(edited)
For example... The percentage of holdings that are dominating an EP open (>=70% equity on each street)
Preflop: 2.1%
Flop: 21.5%
Turn: 27.7%
River: 33%(edited)
It seems like you can't properly breakdown the equity AND have the correct bet-sizings w/o having most holdings be fractionally flats/3bets because there are too many unknowns (namely, the entire board)
whereas, after the flop, you can make more informed decisions and have few or no holdings that are played differently in the same situation
It seems like you're gaining some EV on the polarized parts of your range, in exchange for losing some EV in the condensed parts... And, I would argue, that you are losing more than gaining because of all of the information on the flop. Also, you can still get all-in with the best holdings on a SRP, so, you're not losing out on the EV with your best hands.

With dominating hands being hands that have 70% or more equity against the opponents range.

Isn't your post also an argument for why you would want to fold out hands preflop with a 3bet?

I mean if some hands that have poor preflop equity relative to my range make better hands by the river than why would I want to flat and allow that to happen?