There was definitely a clear progression, building towards more and more equality and Sirtis paved the way for that, it's true. Ripley in Alien was great, and even Lambert, despite being a scared mess in the later stages, was an officer, a navigator, and clearly well trained in the first half.
It's remarkable how often the actresses in real life are far more accomplished than their futuristic characters in many ways. Even back in TOS the actresses would have loved to get in on the action but we're instead portrayed as space waitresses. Let's not forget Picard's merry men...
Deanna is very accomplished (and didn’t wear her cleavage top for half as long as people seem to think. Let’s not forget her grey outfit, maroon outfit etc in all this. An honourable mention to the ridiculous male outfits too, with muscles padding and spandex cling to the parts other beers cannot reach. Oh. And Wesley.) and actually does a lot in TNG, even before she ends up in Duty Regs. I think it’s also a mistake to downplay the ‘female’ aspect in female characters. What makes so many of those later characters work so well, is that they are allowed to be television females as well as the more ‘progressive’ aspects. B’Ellanas pregnancy and relationship with Tom is a beautiful example of that, especially with the lampshading of fifties sitcom stuff with those two. Troi is absolutely the beginning of that, in here relations ships with Crusher, Yar, Riker and Chocolate. She wasn’t portrayed as shakey in command stuff because she was a woman...that was because it suited the character at that time (you can also looks at something like Disaster, and contrast her character with Ensign Ro.) Her mother is also an interesting creation in relation to that...we are so used to seeing Data in the Spock role for TNG, but actually, it’s Deanna. Ambassador parent? Half human? Outsider looking in? Struggling with emotional control...well yes, except they flipped it. Deanna is in no way a sexist caricature, because, thank god, Trek never really does that with its lead characters. Sit her next to her most logical opposite number...Will Riker...now examine how the two are treated or objectified as characters. It’s pretty even.
Sirtis puts in a lot of work, particularly early on, and I think too much is made of ‘That Dress’ when thinking about the character. Troi wasn’t nearly ditched because she was female, I think, but because they had accidentally created too complex a character to easily write for, week in week out. We see exactly the same thing happen with Jadzia Dax, and (in a much much weaker way) Kes later on. I was never Deannas greatest fan, particularly when I first watched TNG...but I think it’s a disservice to lots of people to characterise fandoms or the writers issues with the character to come down to gender, especially in the context of the time and audience. Let’s not forget, ‘teenage boys’ were probably Treks golden market for a very long time, for good or ill...but Trek fans were the secondary market, and the most prominent of those were often women. (Not to mention the biggest names in written Trek in those days too.) Trek then was, if anything, more progressive than it is now. Because back then, 45 minutes focussing on a female lead in Treks target demographic was unbelievably unlikely, particularly for an SF or action show (due exceptions to stuff like Wonder Woman in a vaguely related field) in those days, yet we can all point to the Troi episode, or the Crusher episode. (Apart from the usual Hollywood racism, what’s wrong with Sub Rosa anyway? Anne Rice, you may not respond.)
This is the era of Knight Rider, Streethawk, The A-Team.....and here’s TNG.....it’s night and day, even with Berman having to toe the company line in a very different environment to now (back when you really didn’t piss off the Bible Belt too much, and small c conservatism was the order of the day to keep your show on the air.) where we can have DSC making it’s great proclamations of envelope pushing...even though everyone else is on email. (Gay ensemble character? Sorry DSC, Killjoys did that last week, Buffy last millennia. Female lead? African American lead? You may have heard of DS9 and Voyager.)
It’s fun a and exciting having Trek back on air, but Marina Sirtis here was part of the vanguard for this stuff, way back when they genuinely didn’t know what to do with this stuff, and the audience for it was barely there. Fired? Nah. But she nearly didn’t get her contract picked up. That changed, and I think the producers of Trek at that time, and Sirtis, and the character, all deserve a little more credit for doing what they did back then. *shrug*
Once upon a time, SF fans didn’t give much of a monkeys, as long as something cool or interesting was going on. But the discussions these days...I sometimes wonder if I dreamed characters like Aeryn Sun, or indeed Deanna Troi, heir to the chalice of Riix etc etc.
Simple things pleasing simple minds and all that 
