That could very easily be missing out on quite a bit of equity in the long run depending on how villain plays his hands out postflop. T9s in my opinion there is just as good as KJo. They are both marginal hands, and if you're playing against a calling station, then either one of them can be profitable postflop depending on what his postflop stats are. If he is folding to CB's 80+% of the time when a pot was raised preflop, then I am willing to go even more marginal, because I can easily take it away postflop. If he is calling down everything and/or repopping you postflop and it's hard to get an idea of what he has, then I will tighten that preflop 3B'ing range up.
KJo is much stronger than T9s against an opponent with a wide range.
If you hit a king or Jack you probably have the best hand and can value bet 2-3 streets.
If you hit a ten or 9 with T9s then you cant easily value bet it and expect to get called down with weaker tens or nines.
The whole "its suited" argument really dosent boad well at micros. The advantage of these hands is that you can barrel with equity. The problem is if your oponent dosent fold well then you are owning yourself by allowing him to call down with weak made hands whilst yo barrel draws.
So T9s is a good hand to 3bet against an opponent who folds a lot to 3bets, if called you figure you are behind but occasionally will hit a concealed monster.
KJo is a better hand to flat with when your opponents range is wide and he is either very aggro (will
bluff cards that hit you) or very passive (will call down with weaker hands)
What you must take into account is that KJo is behind most peoples opening range (but not vastly so) so you need a postflop plan. You cant call folp bets to decide what to do on the turn or river, you need to know now what to do against this specific opponent.
This can be contrasted to a hand like KK or AA where cards strength is so much greater that calling or raising most flops is rarely a mistake and so you can get deeper into the hand before making big mistakes, and of course by then you have more information.
3betting KJo is never a mistake against someone who folds alot as its a bluff with blockers but calling and playing postflop is always much more profitable provided you can identify why and when its profitable to continue.