Blocked emails and Junk email still show in mail folders and smart mail folders in Apple Mail. Is there a way to delete these so they don't show up in my inbox?

What are your Junk Mail settings? It sounds like you have chosen to “Mark as junk mail, but leave it in my Inbox”, which is exactly what it is doing.

https://support.apple.com/guide/mail/reduce-junk-mail-mlhlp1065/mac

Bounce back has long ago been abandoned since most spam is just using a "Spoofed" email address and never goes back to the actual spammer, further perpetuating Junk Mail being sent across all mail servers. Not only would you see the junk mail, but you would also get another email saying your Bounce Back could not be delivered.

For a Smart Mailbox, add the rule "Message is not in Mailbox" and select "Junk/Trash". Otherwise the Smart Mailbox with a rule such a Today is going to include all emails received today and that would include junk emails. There are many different rules that can be applied to a Smart Mailbox to tailor it exactly like you want.

The Junk Mail options in Mail Settings apply to your Inbox, not a Smart Mailbox where you have created a completely different set of rules for the emails to be shown there.

The first thing you need to do is to make sure that, if it is available, the junk mail filters in your ISP mail server have been set correctly. Log in to your webmail and check the settings for Junk Filters. If you can stop it getting through in the first place then you'll have less to deal with. I've set mine up and I get less than a dozen junk mails a day.

As for "By definition, if you have to write your own code (a rule or a "workaround") then the programming does not work." - what you mean is that it doesn't work for you. That's the point of having a powerful computer - it arrives with a basic set of apps and functionality which are almost infinitely tweakable with programming, macros, rules, configurations, etc. So if you don't like something then it's probably possible to change it to the way you want it. You might have to spend time learning how, but nothing's for nothing. I'm happy with Mail's junk settings. I've set Mail to move anything that my ISP marks as junk to the Junk folder. I check it once a day to make sure nothing I want has found its way there then I run a script which forwards them all to the UK Gov Phishing Reporting address and then deletes them.

BTW - bouncing back to sender is a bad thing. It lets the sender know they've got a live email address and it gets sold on.

Yes, there is an option to send blocked emails to the trash automatically as seen here:

The choice to use a Smart Mailbox is yours and by default there are none. The only reason they exist if for those users who do want to apply rules to display the emails exactly how they want to see them. If you only apply a rule to view the emails from Today, then you will see every email that was received today including Blocked and Junk emails.

It really is not that difficult. If you don't want to deal with a Smart Mailbox, then delete it. You are then left with the simple Inbox, Sent, Trash, Junk, and Draft folders. You will likely find this is much simpler to manage and with those Settings previously described for Junk and Blocked emails, you will no longer see them in your Inbox and there is nothing else that you need to manage.

If you weren't so set on Apple designing a bespoke Mail solution just for you then you could fix this pretty easily. It's easily fixable and if you were more polite, less sarcastic then I'd be minded to help.