Is it ok to keep MacBook plugged in all the time

It is a balance between two competing considerations.

1. Rechargeable Lithium batteries have a service life which can be considered as the number of full charge-discharge cycles. If you use the battery once from full to zero then recharge, or twice down to 50% then recharge - that is one full cycle of the hundreds it should be able to produce. The charging function shuts down at full charge and the external charger brick just functions to keep the computer working instead of the battery being used. Naturally this means you could keep the computer plugged in and alive for weeks without using any of your charge cycles. BUT the battery would be held at 100% charge condition.
2. Lithium batteries store best around 40-60% of fully charged. Above or below this they tend to age slightly faster (and if you go to 0% charge they age really fast if not recharged promptly).

Now you can see it’s a balance between holding at 100% but not using charge cycles, or using the battery to avoid sitting at 100% but using charge cycles. No easy answer to that one, every usage is different.

From personal experience I tend to keep my batteries toward the top of charge if possible and I have never noticed bad effects. It means I have maximum endurance when I’m forced to use battery. The exception to that is my Apple Watch which gets charged every evening then lives on my wrist overnight and next day. It is still showing the same daily drop to 60-70% since it was new 3 years ago.

It can, but it also may not. This is an often debated question. It is more likely to shorten the life if you are constantly plugging in and removing the adapter. When it is constantly plugged in it manages the power steadily. Make sure to use in a well ventilated area that doesn't get overheated and the power cord does not get frayed and is the right wattage for your model. Do not use the L shaped pullouts on the brick to wrap the cord as it is easy to get the cord frayed that way.

It’s a Yes from me.

I do this all the time as I rarely use my mid-2012 MacBook Pro on battery alone. It still has the original battery it came with and it’s still “healthy”, ie no Service Recommended warnings. Admittedly I now only get about an hour of battery use out of it, which, I think, is pretty good for an 8-year old battery.

its something I’ve always done with all the laptops I’ve used since 2006.

My 2p