Well lets see, in a whole day right the entire LTC and DOGE networks bring in a total of $1.58 million dollars combined.

Bitcoin, from *fees alone* without any inflation brings in $1.72million dollars/day.

This means that even with inflation completely gone in Bitcoin, Bitcoin already brings in enough in fees pay for significantly more security than those two altcoins achieve essentially entirely from inflation.  (You could, for whatever it's worth add other semi-popular altcoins to that and still be less than Bitcoin, I just used the two you suggest)

"Merged mining" is significantly undermined by the central game theory argument for mining:  The game theory argument for mining is that to mine you expend costly energy, and if your work won't end up in the longest chain (or you manage to blow up the thing you're mining) then that effort is wasted so it is in your best interest to mine honestly.

In the case of merge mining if one asset has meaningful income (like dogecoin maybe has with its perpetual inflation) and the other asset does not-- like litecoin once is subsidy is depleted (unless something changes). Then only the income side has meaningful security, the non-income side does not because the attacker isn't losing much if his blocks don't end up on the longest chain or if he sets the whole thing on fire.

Maybe you can see why many Bitcoiners really dislike altcoiners.  It's usually not that they have any issue with the altcoin itself, it's because people with some kind of investment in the altcoin glibly spread misleading claims about Bitcoin in order to rationalize, justify, and promote their altcoins.

There may well be reasons that you could advocate ltc+doge,  but fudding Bitcoin about its ability to fund security with fees is not one of them.  If Bitcoin's *current* fee-only income isn't enough security income for your taste than you should conclude that these other coins are *currently* insecure and lack any kind of trajectory to allow them to achieve even their current level of security in the future (after all, even doges perpetual inflation effectively dilutes the mining income down to nothing over time too; just at the cost of also debasing everyone's holdings at the same time).