SG-1, compared to many other overdone shows, had one redeeming quality - the protagonists (in this case, all humans) actually progressed through the course of the show. In SG-1 humans went from 1980s level of technology in Season 1 to spaceships, teleporters and off-world colonies in Season 10. So new 'bigger bad' always made some kind of sense, and I feel there was a space for a few seasons worth of additional interesting ideas.
That, or they could have simply continued Stargate: Universe.
There is one series I'm really up in arms about it being recently cancelled - Person of Interest. That one was nowhere close to repetitive, it had tons and tons of space for good, intelligent story developments, and it got cancelled behind the crew's back anyway, because whatever. Fuck you, CBS, for cutting out what was probably the only thing in history of television that approached the topic of AI in a smart, realistic way (and also basically broke Snowden's revelations a year before Snowden).
The loss of RDA which was a major part of the appeal of the show and the constant attempts to replace/clone him for every show in the franchise afterwards was pretty lame.
The constant rotation of the supporting cast also did not really help the show, and the move from a procedural format with a few long term plot lines to a fixed seasonal story arc also didn't really help the show to maintain (it's weekly) audience (most fans would agree that the Showtime seasons were the best).
I did chuckle at the Farscape fan service they did in the later seasons, and there were a few fun moments but overall the show was pretty much dead around season 7.
They should've let SG1 go and spun it to a few other shows, but sadly SyFy (or how ever they spell their name now) wanted to dumb things down and make it flashy and splashy which is why SG: Atlantis looked more like Sharknado than SG1. By the time they tried to bring things back to the roots with SGU they still mocked it up, SyFy promoted SGU as a worthy replacement to Battlestar Galactica and tried to appeal to it's fan base with pretty disastrous results.
For example how Star Trek explored early space exploration in Enterprise (sans time traveling shenanigans), another era in the original series, and another one in The new generation and DS9 and Voyager.
I do like the stargate universe, the Atlantis spin-off in particular, and I would like to see more of it. Maybe they can set a new series in, say, 100 years from the ending of SG1. Or maybe it is time to move on to fresh ideas. I liked the universe of The Expanse, for example, and am looking forward how they can move it forward.
(I was less happy about the Dark Matter universe, or rather the story told in it, for example: one small ship with a small crew holding the balance and future of the entire (known) universe in their hands is a bit too much for me.)
I like The Expanse too, I'm waiting for the second season, and seriously considering picking up the books it's based on.
The fact that CBS let this one drag on forever without anybody watching it and after losing Taraji P. Henson to Empire (which was crippling) so it could have a proper ending IMO is something to praise them for rather than damn them.