Alright!

Defensively:

There are a few problems with your shape. The first thing that I notice is the engagement line. The most important part of setting your engamgement line is to think about whether its more important to pressure their midfield, or constrict space between your midfield line and defensive line. In the 42121 you have a combination of high line + lower line of engagement. This is most useful for tactics without a CDM. Your tactic has two. This means that you are doubling down on restricting space that your formation already limits. If they have a CAM you'll completely cut them out of the game, but their CMs and CDMs will be free to play balls over the top to their wingers or their striker. With your tactic set up like this you will concede a lot of goals to a 442 or any wide formation without a CAM. Also your backline better have crazy speed and anticipation to make high line/low engagement work.

Its fine to have an offensive gameplan that you more or less stick to. But it is usually best to tailor your defense to each opponent. Think about where on the pitch their players are going to be, and how to get your players to limit that space. Also, more generally, don't try to defend where they are scoring from, defend where they are assisting from. Your biggest goal in defense is to sever their most important connections.

Offensively:

Turn off play for set pieces. I don't care if your CBs are 6'6 that instruction has never been good.

The combination of pass into space and more direct passing will make games extremely chaotic and is only, if ever, suitable in limited circumstances.

Don't use AP in the AML/R spots, or WP, they have never been good.

whipped crosses aren't a great team wide instruction. They require extremely high technique and crossing to do well. Only use that instruction for your best crossers.

Playing with two defensively focused midfielders is usually bad. If you need to have two CDMs because of squad construction try putting one on Volante or roaming playmaker.

throw it long without also have distribute quickly is probably not good.

don't have overlap on the side with a Winger. It defeats the whole purpose of the role. Overlap is generally only good when your FB is a better dribbler than your wide player. The instruction basically tells your wide AML to dribble less, hold up the ball, and look for the FB making a run. Unless your winger is heavily outmatched by their FB you're slowing down your attack for no benefit.

Overall:

This site rates tactics by using them to simulate games. Look at the top 10 or 20 tactics and see what all of them or none of them use in their tactics. You can play how you want but in every edition there are overall strategies and individual roles or instructions that just don't work. A few things I'm seeing for the most recent FM24 patch is 2CDMs and 2 strikers with low crosses. You don't need to change your tactic completely but its good to check and see what can apply to your tactic. Often times things like playing the offside trap, stopper/cover duty, overlap/underlap, certain striker roles, having 1 or 2 strikers, or certain fullback roles, either don't work at all or are super OP.

it is sometimes ok to have a mostly unchanging offensive approach. But, how you build out from the back and your defensive shape should probably change every match. Some teams force the ball wide, there is no need to have a stacked midfield. Some teams force the ball through the middle, there is no need to have a wide shape. Some teams have tiny players on their defensive line, don't be afraid to have your GK play long if you are having issues at the back. Some teams won't have players marking your wingers or FBs in your own half, don't be afraid to change your distribution to accommodate that.

Develop 1 tactic that is your overall best practice, 1 tactic for breaking down low blocks, and 1 tactic for when you lose the midfield badly. Give each a different defensive shape so that you can switch between them as needed during matches without penalty.

Developing the perfect tactic is not as important as developing the perfect tactic for your players. Even if your desired playstyle, or the current fm "meta," is to use overlaps and whipped crosses, you should only do it if you have great dribbling and crossing FBs. Set individualized tactics if thats what is needed.

Usually in FM the most effective strategies will heavily exploit the channels, low crosses, cutbacks, and square balls. Literally this has been true for a decade. Play how you want, but keep that in mind if all you care about is winning.