monitoring resources used by apps

<< I've tried looking at Activity Monitor but its short time slices mean that I can't easily see what's going on. >>

I think you may be mistaken. Activity monitor does not just buzz in, sample for two microseconds and let everything else go by. it only updates the display periodically, but when its window is open, it is tabulating everything.

Activity monitor does what you are asking for.

on Activity Monitor's Memory display, is memory pressure completely GREEN?

any compressed memory?

Any Swap Used? (this is a high-water-mark indicator that is very slow to recede)

But I have a larger question:

If you confirm your belief that this web site uses a lot of resources. what can you do with that information?

The most important reason your Mac is somewhat slow is shown clearly in the graphs and tables above. Memory pressure is not yet choking, as shown by the box still green. But it is too high for high responsiveness, indicated by the graph more than a quarter full.

Memory is staring to get scarce, indicated by your Mac has started to Compress items still cached in memory to save space. 1.64 Gb is now holding compressed items. This allows your Mac to gain more space in RAM memory, at the expense of a small amount of compute-time to de-compress for use.

The strongest indicator of slowing things is that at some point recently, your Mac was so short of real RAM memory that is spilled some of the contents RAM onto the boot Drive into a Swap File. 2.83 GB is now being simulated in a disk file on the boot drive. That is FAR slower than real RAM.

The size of the Swap File indicates the worst-case severity of the shortage. Slowly, over time, if RAM became plentiful again, the size of the swap file is designed to be reduced. But if the shortage stays the same or grows, more and more and more things end up being swapped out, and reduced from RAM access times to Drive access times - over 1000 times slower.

Opening multiple tabs on web browsing can consume resources a lot.

Having over 85% of your hard drive full, or synchronizing with the Cloud or Time Machine can eat a lot of your resources.

Try different web browsers:

Browsers by Mac operating system - Apple Community

I used to post that MacOS after El Capitan required MORE than 4GB of Real RAM to run in an appropriately responsive way. After Mojave, that number has gotten closer to 8G of real RAM, and after Ventura, MORE than 8GB or real RAM is needed just to run MacOS in an appropriately responsive way. This assessment is NOT adding in a big fat Web Browser and busy Web pages with moving ads and videos -- that's just MacOS.

The answers are above. Your Mac does not have enough real RAM for all the things you are doing at the same time.

your memory has become so full that your Mac is simulating needed RAM on the boot drive, which is FAR slower than real RAM.

if you have Chrome open, even if it is doing nothing, it remains the biggest resource hog that is not obvious malware.

Not all Macs ever produced are equal. Yours is now more than ten years old, and you are comparing to a brand new ChromeBook. A more realistic comparison would be to compare to a new MacBook Air with MORE than 8 GB RAM.

To clear out the logjam temporarily, Restart your Mac.

Immediately look at those memory number for a baseline, before you launch ANY apps. That will tell you what your best case can be.

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More modern Macs have drives that are Faster than the drive in this Mac, so having a swap file on a more modern Mac is not as slowing. Today's Macs can run their Boot drive near 5,000 M Bytes/sec, while your drive, a very early SSD, may be running under 500 M Bytes/sec.

Are you running the original drive?

if a replacement SSD drive, have you enabled TRIM?

Can enabling TRIM be done without risking information on the drive?

<<Can enabling TRIM be done without risking information on the drive? >>

Yes, the Mac uses a method that has a very light touch, and horror stories of data loss woes are not seen here.