Arcs aren't the problem, it's the planning and the pacing that are the problem.
I agree, you should make your Season Finale, adaptable to be a Series Finale if necessary, and try to clean almost everything up from this season by the end of it, and start to unravel something for the next season.
So, you need to know going in, what you want to accomplish, where you want to go, and how long you will take to get there, and it shouldn't be so closed ended that you can't either do more seasons with a new arc or do a spinoff in the same universe. The Network needs to understand this arc is planned for X number of years, and that taking it longer than that will water the show down, but, they need to know if it's a hit, they'll be able to milk it longer via a spinoff, or a new arc (IE: A 5 year gets to end, show is still real strong, present them with a follow story of at least two years, and have them guarantee that 2 years, so your audience who has stuck with you through 5+ years doesn't get shafted; or have a spinoff idea ready to offer them if you can't continue the primary show)
The frenetic pace, unfortunately is necessary for today's audience, they don't want to watch a show not move along arc-wise each week, unless there is a "Shiny Gold ball to attract their attention". I do agree, you shouldn't throw out 15 plotlines and advance each one only 1 or 2 minutes a week. You do need to pace properly. Throw 3 or 4 or 5 plotlines, let them develop each week, and lead into the next 3 or 4 or 5 as they resolve themselves. As well as planning your arc by the season, you also need to plan it according to rerun breaks. If Plotline A leads to plotline D, don't throw plotline D out on day 1 and let it languish for a year, let Plotline A play itself almost out, and open up the reveal of plotline D, you still get there in the same amount of time, but, it's much more entertaining to watch it unfold.
Maybe 22 - 26 episodes a season, is a burden, 13 episode seasons often have much tighter arc pacing
And of course, you need characters the audience can relate to, cheer on, love to hate, or something that entertains them and keep the characters growing. I think SGU's biggest problem for me was I couldn't enjoy any of the characters for the first season. Rush, Greer and Young, I thought really hurt the show, there was nothing that made me want to watch those characters (Though by second half of Season two I really enjoyed Rush and Greer, and I absolutely love the character Mr Gold/Rumplestiltskin on Once Upon a Time, so, it's certainly wasn't the actor in the case of Rush, it was writing). Nothing wrong with having a character or two you don't like or want to see get killed, that makes the show better and give you drama and tension to play off. But, when you want to see the entire cast blown up, there's something wrong with the character writing